Tetromino

$\begin{figure}\begin{center}\BoxedEPSF{Tetrominoes.epsf scaled 1000}\end{center}\end{figure}$

The five 4-Polyominoes, known as Straight, L-, T-, Square, and Skew.

References

Gardner, M. ``Polyominoes.'' Ch. 13 in The Scientific American Book of Mathematical Puzzles & Diversions. New York: Simon and Schuster, pp. 124-140, 1959.

Hunter, J. A. H. and Madachy, J. S. Mathematical Diversions. New York: Dover, pp. 80-81, 1975.