A234012 Number of unbiased free polyominoes with 2n squares.

1, 4, 24, 230, 2601, 32810, 433855, 5923677, 82675193, 1173878266

Offset: 1

Author

John Mason, Dec 18 2013

Keywords

• nonn
• more

Comments

Define the bias of a polyomino to be the difference between the number of black squares and the number of white squares when chessboard coloring is applied to the polyomino. Unbiased polyominoes are those having an equal number of black and white squares. The sequence is defined for 2n rather than n as odd-sized polyominoes are obviously biased.

Links

• Herman Tulleken, Polyominoes 2.2: How they fit together, (2019).

Crossrefs

Cf. A000105, A001933.

Extensions

a(9)-a(10) from Sean A. Irvine, Aug 22 2020