# Tetromino-Pentomino Compatibility

## Introduction

A *tetromino* is a figure made of four squares joined edge to edge.
A *pentomino* is a figure made of five squares joined edge to edge.
There are 5 tetrominoes and 12 pentominoes,
not distinguishing reflections and rotations.
They were first enumerated and studied by Solomon Golomb.
The *compatibility problem*
is to find a figure that can be tiled with each of a set of polyforms.
Polyomino compatibility has been widely studied since the early 1990s,
and two well-known websites, Poly^{2}ominoes by Jorge Mireles and
Polypolyominoes by
Giovanni Resta, present the results of their authors' systematic searches
for compatibility figures.
The sites include solutions by other researchers, especially Mike Reid.
So far as I know, polyomino compatibility has not been treated in print
since Golomb first raised the issue in 1981,
except in a series of articles called Polyomino Number Theory,

written by Andris Cibulis, Andy Liu, Bob Wainwright,
Uldis Barbans, and Gilbert Lee from 2002 to 2005.

Here I show minimal known tetromino-pentomino compatibility
figures, allowing or disallowing holes.
If you find a smaller solution or solve an unsolved case,
please let me know.

The largest solution, for the square tetromino and the T pentomino,
was found by Helmut Postl.

For compatibility of two pentominoes with or without holes, see
Pentomino Compatibility.
Resta's page of tetromino-pentomino compatibilities was originally
on GeoCities, a defunct web host.
It is now
here.
Mireles's site was also on GeoCities and has not been rebuilt.
The link above is to the Internet Archive.

## Tetromino Names

These are Livio Zucca's names for the tetrominoes:

## Pentomino Names

These are Golomb's names for the pentominoes:

## Solutions Allowing Holes

### Table

This table shows the smallest number of tiles known to suffice
to construct a figure tilable by the tetromino and the pentomino.

| F | I | L | N | P | T | U | V | W | X | Y | Z |

I | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 8 10 | 8 10 | 8 10 | 4 5 | × | 4 5 | 8 10 |

L | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 8 10 | 4 5 | 4 5 |

N | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 8 10 | 4 5 | 4 5 | 4 5 | 8 10 | 4 5 | 4 5 |

Q | 8 10 | 4 5 | 4 5 | 4 5 | 4 5 | 112 140 | 64 80 | 4 5 | 16 20 | × | 8 10 | 4 5 |

T | 4 5 | 8 10 | 4 5 | 8 10 | 4 5 | 4 5 | 8 10 | 8 10 | 8 10 | 4 5 | 4 5 | 8 10 |

### Solutions

## Variants Without Holes

### Table

This table shows the smallest number of tiles known to suffice
to construct a holeless figure tilable by the tetromino and the pentomino.
Shaded cells indicate solutions that are minimal even if holes are allowed.

| F | I | L | N | P | T | U | V | W | X | Y | Z |

I | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 8 10 | 8 10 | 8 10 | 4 5 | × | 4 5 | 8 10 |

L | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 8 10 | 4 5 | 4 5 |

N | 4 5 | 4 5 | 4 5 | 4 5 | 4 5 | 8 10 | 4 5 | 4 5 | 4 5 | 12 15 | 4 5 | 4 5 |

Q | ? | 4 5 | 4 5 | 8 10 | 4 5 | ? | ? | 4 5 | ? | × | 8 10 | 4 5 |

T | 4 5 | 8 10 | 8 10 | 8 10 | 4 5 | 4 5 | 8 10 | 8 10 | 8 10 | 8 10 | 4 5 | 8 10 |

### Solutions

Here I show only solutions that are larger than the
corresponding minimal solutions allowing holes.
So far as I know, these solutions
are minimal. They are not necessarily uniquely minimal.

Last revised 2014-09-01.

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Col. George Sicherman
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