OFFSET
1,1
COMMENTS
Chessboard-colored polyominoes, considering to be distinct two shapes that cannot be mapped onto each other by any form of symmetry. For example, there are two distinct monominoes, one black, one white. There is only one domino, with one black square, and one white. - John Mason, Nov 25 2013
REFERENCES
W. F. Lunnon, personal communication.
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).
LINKS
John Mason, Table of n, a(n) for n = 1..50
Joseph Myers, Chessboard polyominoes
FORMULA
CROSSREFS
Cf. A001071, A000105, A121198, A234006 (free polyominoes of size 2n that have at least reflectional symmetry on a horizontal or vertical axis that coincides with the edges of some of the squares), A234007 (free polyominoes with 4n squares, having 90-degree rotational symmetry about a square corner, but not having reflective symmetry), A234008 (free polyominoes with 2n squares, having 180-degree rotational symmetry about a square mid-side, but no reflective symmetry).
KEYWORD
hard,nonn
AUTHOR
EXTENSIONS
a(14)-a(17) from Joseph Myers, Oct 01 2011
a(18)-a(23) from John Mason, Dec 05 2013
a(24)-a(30) from John Mason, Dec 23 2021
STATUS
approved