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A234012 Number of unbiased free polyominoes with 2n squares. 1
1, 4, 24, 230, 2601, 32810, 433855, 5923677 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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

Table of n, a(n) for n=1..8.

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

CROSSREFS

Cf. A000105, A001933.

Sequence in context: A216857 A318005 A224800 * A244760 A240403 A074598

Adjacent sequences:  A234009 A234010 A234011 * A234013 A234014 A234015

KEYWORD

nonn,more

AUTHOR

John Mason, Dec 18 2013

STATUS

approved

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Last modified February 28 10:22 EST 2020. Contains 332323 sequences. (Running on oeis4.)