Polyform Curiosities

A polyform is a geometric shape formed by joining copies of a single shape. The best known polyforms are polyominoes, made from squares. Solomon W. Golomb coined the term, studied polyominoes extensively, and published a book about them. Other plane polyforms include polyiamonds, made from equilateral triangles; polyaboloes or polytans, made from isosceles right triangles; polyhexes, made from regular hexagons; and polylines or polysticks, made from straight lines. Solid polyforms include polycubes, polyominoids, and polyrhons.

  • Remembrance of Software Past
  • Exclusion
  • Tiling
  • Tetrads
  • Compatibility
  • Ordinary Compatibility
  • Galvagni Compatibility
  • Baiocchi Figures
  • Cell Shifting
  • Oddities
  • Catalogues
  • Printable Grids
  • Wallpaper
  • Links
  • Acknowledgments

  • Remembrance of Software Past

    It isn't trivial!  —Livio Zucca

    From 1999 to 2005 Livio Zucca maintained a vast website of mathematical recreations called Remembrance of Software Past. It was full of new ideas, attracting contributions from many talented mathematicians. Unfortunately, it was hosted by GeoCities, which was shut down in 2009. Fortunately Giovanni Resta reconstructed Remembrance in full on his host Iread.it.

    Deteriorating eyesight left Livio unable to maintain his site. With Livio's permission I have revived his Remembrance pages about polyomino compatibility. I have updated the links and many of the solutions. Livio and I welcome new contributions. If you would like to submit an improved solution, or a new solution, or a new idea, please write me at colonel@monmouth.com.

    Pento-Tro-Dominoes. Find a figure that can be tiled with any of a given pentomino, tromino, and domino.
    Pento-Tetro-Trominoes. Find a figure that can be tiled with any of a given pentomino, tetromino, and tromino.
    Tetrominoes Challenge. Find a figure that can be tiled with each of a given set of tetrominoes and no others.
    Triple Pentominoes. Find a figure that can be tiled with each of three given pentominoes.
    Pentomino Odd Pairs. Find a figure that can be tiled with an odd number of either of two pentominoes.

    Exclusion

    No room! No room! they cried out when they saw Alice coming.

    —Lewis Carroll, Alice's Adventures in Wonderland

    The exclusion problem is to remove as few cells as possible from a given figure or the plane so as to exclude a given polyform.

    Hexomino Exclusion. Exclude a hexomino from a checkerboard.
    Polyiamond Exclusion. Exclude a polyiamond from the plane.
    Polyhex Exclusion. Exclude a polyhex from the plane.

    Tiling

    The slabs made a most intricate and fascinating design, but a thoroughly unobtrusive one, unless one paid deliberate attention to it.

    —Carlos Castaneda, The Second Ring of Power

    The tiling problem is to join copies of one or more polyforms to make a given polyform.

    Polyiamond Hexagon Tiling. Tile a straight or ragged hexagon with various polyiamonds.

    Tetrads

    Then clap four slices of pilaster on 't,
    That laced with bits of rustic makes a front.

    —Alexander Pope, “Epistle to Richard Boyle”
    Tetrads. A polyform tetrad is four copies of a polyform, joined so every copy shares a boundary with every other.

    Compatibility

    A maddening identity of the big picture is arrived at without using any similar pieces.

    —Arpad Arutinov, The Back Door of History

    Ordinary Compatibility

    The Compatibility Problem is to construct a figure that can be tiled with each of a set of polyforms.

    Polyominoes

    Pentomino Compatibility. Given two pentominoes, construct a figure that can be tiled with either.
    Holeless Hexomino Compatibility. Given two hexominoes, construct a holeless figure that can be tiled with either.
    Tetromino-Pentomino Compatibility. Given a tetromino and a pentomino, construct a figure that can be tiled with either.
    Holeless Tetromino-Hexomino Compatibility. Given a tetromino and a hexomino, construct a holeless figure that can be tiled with either.
    Holeless Pentomino-Hexomino Compatibility. Given a pentomino and a hexomino, construct a holeless figure that can be tiled with either.
    Square Enneiomino Compatibility. Which polyominoes are compatible with the square enneiomino?
    Voided Square Octomino Compatibility. Which polyominoes are compatible with the square octomino with a hole in it?
    Holeless Triple Pentominoes. Holeless solutions for Livio Zucca's Triple Pentominoes.
    Holeless Pentomino Odd Pairs. Holeless solutions for Livio Zucca's Pentomino Odd Pairs.
    Pentomino Odd Triples. Like Livio Zucca's Triple Pentominoes, with an odd number of tiles.
    Multiple Polyomino Compatibility. Figures that can be tiled by many polyominoes of the same order.

    Polyiamonds

    Hexiamond Compatibility. Given two hexiamonds, construct a figure that can be tiled with either.
    Triple Hexiamonds. Given three hexiamonds, construct a figure that can be tiled with each.
    Heptiamond Compatibility. Given two heptiamonds, construct a figure that can be tiled with either.
    Octiamond Compatibility. Given two octiamonds, construct a figure that can be tiled with either.
    Mixed Polyiamond Compatibility. Given two polyiamonds of different orders, construct a figure that can be tiled with either.
    Multiple Polyiamond Compatibility. Figures that can be tiled by many polyiamonds of the same order.

    Polyhexes

    Pentahex Compatibility. Given two pentahexes, construct a figure that can be tiled with either.
    Pentahex Odd Pairs. Given two pentahexes, construct a figure that can be tiled with an odd number of either.
    Mixed Polyhex Compatibility. Given two polyhexes of different orders, construct a figure that can be tiled with either.
    Seven Euphoric Pentahexes. Each of these pentahexes is compatible with all 82 hexahexes.
    Three Euphoric Hexahexes. Each of these hexahexes is compatible with all 82 hexahexes.
    Ring Hexahex Compatibility. Which polyhexes are compatible with the ring hexahex?
    Multiple Polyhex Compatibility. Figures that can be tiled by many polyhexes of the same order.
    Zucca's Challenge Problem for Tetrahexes. Given a set of tetrahexes, construct a figure that can be tiled with any member of the set and no other.

    Other Plane Polyforms

    Zucca's Challenge Problem. Given a set of polyforms of the same order, construct a figure that can be tiled with any member of the set and no other.
    Pentapent Compatibility. Figures that can be tiled by two different pentapents.
    Mixed Polypent Compatibility. Figures that can be tiled by polypents of different orders.
    Pentahept Compatibility. Given two pentahepts, construct a figure that can be tiled with either.
    Tetrabolo Compatibility. Given two tetraboloes, construct a figure that can be tiled with either.
    Tetrabolo-Pentabolo Compatibility. Given a tetrabolo and a pentabolo, construct a figure that can be tiled with either.
    Tetrahop Compatibility. Given two tetrahops, construct a figure that can be tiled with either.

    Solid Polyforms

    Tetracube Compatibility. Given two tetracubes, construct a figure that can be tiled with either.
    Pentacube Compatibility. Given two pentacubes, construct a figure that can be tiled with either.

    Galvagni Compatibility

    Galvagni's problem is to construct a figure that can be tiled with a polyform in more than one way. A Reid Figure is a Galvagni Figure without holes. A Plover Figure is a Galvagni Figure made without reflecting the polyform.

    Galvagni Figures & Reid Figures for Pentominoes. Galvagni Figures & Reid Figures for Octahexes.
    Galvagni Figures & Reid Figures for Hexominoes. Galvagni Figures for Polypents.
    Holeless Plover Figures for Polyominoes. Galvagni Figures for Polyhepts.
    Galvagni Figures & Reid Figures for Heptominoes. Galvagni Figures for Polyocts.
    Galvagni Figures & Reid Figures for Octominoes. Galvagni Figures for Polyenns.
    Galvagni Figures & Reid Figures for Polyhops. Galvagni Figures for Polydecs.
    Galvagni Figures for Polyjogs. Galvagni Figures for Polyhendecs.
    Galvagni Figures & Reid Figures for Heptiamonds. Galvagni Figures for Polydodecs.
    Galvagni Figures & Reid Figures for Octiamonds. Galvagni Figures for Pentacubes.
    Galvagni Figures & Reid Figures for Enneiamonds. Galvagni Figures for Tetrarhons.
    Galvagni Figures & Reid Figures for Polymings. Plover Figures for Polyiamonds and Polyhexes.
    Galvagni Figures & Reid Figures for Pentahexes. Galvagni Figures for Polylines.
    Galvagni Figures & Reid Figures for Hexahexes. Galvagni Figures & Plover Figures for Tetrominoids.
    Galvagni Figures & Reid Figures for Heptahexes.  

    Baiocchi Figures

    A Baiocchi figure has full symmetry and is formed by joining copies of a single polyform. Most Baiocchi figures involve Galvagni figures.

    Baiocchi Figures for Polyiamonds Baiocchi Figures for Polyenns
    Baiocchi Figures for Polyominoes Baiocchi Figures for Polydecs
    Baiocchi Figures for Polypents Baiocchi Figures for Polyhendecs
    Baiocchi Figures for Polyhexes Baiocchi Figures for Polycubes
    Baiocchi Figures for Polyhepts Baiocchi Figures for Polyominoids
    Baiocchi Figures for Polyocts

    Cell Shifting

    The Cell Shifting Problem is to join copies of a polyform to construct two figures that differ in just one cell, as near as possible.

    Cell Shifts for Polyominoes of order up through 6. Cell Shifts for Pentomino Pairs.
    Cell Shifts for Polyhexes of order up through 5. Cell Shifts for Pentahex Pairs.
    Cell Shifts for Heptominoes. Cell Shifts for Hexahexes.
    Cell Shifts for Polyiamonds of order up through 7. Cell Shifts for Heptahexes.
    Cell Shifts for Octiamonds.  

    Oddities

    That is another of your odd notions, said the Prefect, who had the fashion of calling everything odd that was beyond his comprehension, and thus lived amid an absolute legion of oddities.

    —Poe, The Purloined Letter

    An oddity is a figure with binary symmetry made by joining an odd number of copies of a polyform.

    Polyominoes

    Polyomino Oddities. Oddities for polyominoes of order up to 7.
    Pentomino Oddities. Pentomino oddities with specific symmetries.
    Hexomino Oddities. Hexomino oddities with specific symmetries.
    Polyomino Semi-Oddities. Semi-oddities for polyominoes. A semi-oddity is a figure with quaternary symmetry and an even number of tiles that is not a multiple of 4.
    Heptomino Oddities. Heptomino oddities with specific symmetries.

    Polykings

    Pentaking Oddities. Oddities with specific symmetries for pseudopolyominoes of order 5.

    Polyiamonds

    Pentiamond, Heptiamond, and Enneiamond Oddities. Oddities for pentiamonds, heptiamonds, and enneiamonds. Oddities for polyiamonds of odd order can have only bilateral symmetry.
    Hexiamond Oddities. Hexiamond oddities with specific symmetries.
    Octiamond Oddities. Octiamond oddities with specific symmetries.
    Polyiamond Tri-Oddities. These are like oddities but with ternary symmetry.

    Polyhexes

    Polyhex Oddities. Oddities for polyhexes of order up to 5, with specific symmetries.
    Hexahex Oddities. Hexahex oddities with specific symmetries.
    Heptahex Oddities. Heptahex oddities with specific symmetries.
    Polyhex Tri-Oddities. Tri-oddities for polyhexes of order up to 5.
    Hexahex Tri-Oddities. Tri-oddities for hexahexes.
    Heptahex Tri-Oddities. Tri-oddities for heptahexes.

    Polypents

    Pentapent Oddities. Oddities for pentapents.
    Hexapent Oddities. Oddities for hexapents.
    Heptapent Oddities. Oddities for heptapents.

    Polyhepts

    Pentahept Oddities. Oddities for pentahepts.

    Polyocts

    Polyoct Oddities. Oddities for polyocts of order 1 through 5.

    Polyenns

    Pentenn Oddities. Oddities for pentenns.

    Polydecs

    Polydec Oddities. Oddities for polydecs.

    Catalogues

    It was a strange collection, . . . but so much larger and so much more varied that I think I never had more pleasure than in sorting them.

    —Robert Louis Stevenson, Treasure Island

    Catalogue of Polypents. Enumerations and pictures of these neglected polyforms.
    Catalogue of Polyhepts. Some more neglected polyforms.
    Catalogue of Polyocts. Still more neglected polyforms.
    Catalogue of Polyhops. Thomas Atkinson's hopscotch-style polyominoes.
    Catalogue of Polyjogs. Polyforms formed of squares joined by half edges.
    Catalogue of Polypennies. Polyforms formed by joining disks tangentially.
    Polycube Symmetries. In how many ways can a polycube be symmetrical?
    Catalogue of Polyrhons. Polyforms formed by joining rhombic dodecahedrons.

    Printable Grids

    Something was out to get him, something here, among the paper.

    —Thomas Pynchon, Gravity's Rainbow

    Printable Grid Files. Square, triangular, and hexagonal grids, for those who like to play with polyominoes, polyiamonds, and polyhexes.

    Wallpaper

    My wallpaper and I are fighting a duel to the death. One or the other of us has to go.

    —Oscar Wilde

    Tetromino Wallpaper.
    Pentiamond Wallpaper.
    Tetrahex Wallpaper.
    Dragomino Wallpaper. A Dragomino is the polyomino equivalent of a Dragon Curve.

    Polyform Links

    These roads are all strange—and what a lot of them there are!

    —L. Frank Baum, The Road to Oz

    Livio Zucca's Remembrance of Software Past
    Andrew Clarke's The Poly Pages
    Polyiamonds, at Mathematische Basteleien (in German)
    Miroslav Vicher's Polyiamonds Page
    Iamonds at Ed Pegg's mathpuzzle.com
    Polyominoes and Other Animals at The Geometry Junkyard
    Polyiamond at MathWorld
    Gabriele Carelli's Polyforms (in Italian)
    The September 2004 issue of Erich Friedman's Math Magic, on polyform compatibility
    The November 2004 issue of Erich Friedman's Math Magic, on Galvagni's Multiple Tiling Problem
    Peter's Polyform Pages
    Michael Reid's Polyomino Page
    Giovanni Resta's Polypolyominoes
    Jorge Luis Mireles's Poly2ominoes
    KSO Glorieux Ronse's Pentomino site, established by Odette De Meulemeester
    Rodolfo Marcelo Kurchan's periodical Puzzle Fun
    K. Ishino's Puzzle Page (in Japanese)
    Alexandre Owen Muñiz's Math at First Sight
    Torsten Sillke's Home Page
    Abaroth's Puzzles

    Acknowledgment

    Many of my constructions were found using the computing resources of Netrics.

    Col. George Sicherman [ HOME | MAIL ]