Pentomino
A pentomino is a 5-polyomino. There are 12 free pentominoes, 18 one-sided pentominoes, and 63 fixed pentominoes.
The twelve free pentominoes are known by the letters of the alphabet they most closely
resemble: 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, 
, and 
(Gardner 1960,
Golomb 1995). Another common naming convention replaces 
, 
, 
, and 
with 
, 
, 
, and 
so that all letters
from 
to 
are used (Berlekamp
et al. 1982). In particular, in the game of life cellular automaton, the 
-pentomino is always
known as the 
-pentomino. The 
, 
, and 
pentominoes can
also be called the straight pentomino, L-pentomino,
and T-pentomino, respectively.
Ball, W. W. R. and Coxeter, H. S. M. Mathematical Recreations and Essays, 13th ed. New York: Dover, pp. 110-111, 1987.
Berlekamp, E. R.; Conway, J. H; and Guy, R. K. Winning Ways for Your Mathematical Plays, Vol. 1: Adding Games, 2nd ed. Wellesley, MA: A K Peters, 2001.
Berlekamp, E. R.; Conway, J. H; and Guy, R. K. Winning Ways for Your Mathematical Plays, Vol. 2: Games in Particular. London: Academic Press, 1982.
Dudeney, H. E. "The Broken Chessboard." Problem 74 in The Canterbury Puzzles and Other Curious Problems, 7th ed. London: Thomas Nelson and Sons, pp. 119-120, 1949.
Gardner, M. "Mathematical Games: About the Remarkable Similarity between the Icosian Game and the Towers of Hanoi." Sci. Amer. 196, 150-156, May 1957.
Gardner, M. "Mathematical Games: More About the Shapes that Can Be Made with Complex Dominoes." Sci. Amer. 203, 186-198, Nov. 1960.
Golomb, S. W. Polyominoes: Puzzles, Patterns, Problems, and Packings, 2nd ed. Princeton, NJ: Princeton University Press, 1995.
Hunter, J. A. H. and Madachy, J. S. Mathematical Diversions. New York: Dover, pp. 80-86, 1975.
Lei, A. "Pentominoes."
http://www.cs.ust.hk/~philipl/omino/pento.html
Madachy, J. S. "Pentominoes: Some Solved and Unsolved Problems." J. Rec. Math. 2, 181-188, 1969.
O'Beirne, T. H. "Pentominoes and Hexiamonds." New Scientist 12, 379-380, 1961.
Ruskey, F. "Information on Pentomino Puzzles." http://www.theory.csc.uvic.ca/~cos/inf/misc/PentInfo.html.
Smith, A. "Pentomino Relationships." http://www.snaffles.demon.co.uk/pentanomes/.
Verbuyst, C. "Pentomino." http://home.planetinternet.be/~odettedm/.
Weisstein, Eric W. "Pentomino." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Pentomino.html
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