1,3

A000105(n) + A030228(n) = a(n) because the number of free polyominoes plus the number of polyominoes lacking bilateral symmetry equals the number of one-sided polyominoes. - Graeme McRae" (g_m(AT)mcraefamily.com), Jan 05 2006

Names for first few polyominoes: "monomino", "domino", "tromino", "tetromino", "pentomino", "hexomino", "heptomino", "octomino", "enneomino", "decomino", "hendecomino", "dodecomino", ...

S. W. Golomb, Polyominoes. Scribner's, NY, 1965; second edition ( Polyominoes: Puzzles, Packings, Problems and Patterns) Princeton Univ. Press, 1994.

J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 229.

W. F. Lunnon, personal communication.

W. F. Lunnon, Counting multidimensional polyominoes. Computer Journal 18 (1975), no. 4, pp. 366-367.

Jaime Rangel-Mondragon, Polyominoes and Related Families, The Mathematica Journal, 9:3 (2005), 609-640.

D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191-203.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Toshihiro Shirakawa, Table of n, a(n) for n=0 ..45

Ed Pegg, Jr., Illustrations of polyforms

Eric Weisstein's World of Mathematics, Polyomino

See A006758 for another version. See also A030228 (chiral polyominoes), A000105.

Sequence in context: A099626 A046672 A046866 this_sequence A002214 A100408 A140562

Adjacent sequences: A000985 A000986 A000987 this_sequence A000989 A000990 A000991

nonn

N. J. A. Sloane (njas(AT)research.att.com), hugh(AT)mimosa.com (D. Hugh Redelmeier)