A351142 - OEIS

A351142

Free chiral polyominoes with n squares, having 90-degree rotational symmetry about the center of a square of the underlying square matrix.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 0, 0, 3, 7, 0, 0, 14, 25, 0, 0, 55, 90, 0, 0, 216, 319, 0, 0, 816, 1136, 0, 0, 3098, 4088, 0, 0, 11711, 14868, 0, 0, 44462, 54526, 0, 0, 169213, 201527, 0, 0, 646441, 750169, 0, 0, 2477819, 2809931, 0, 0, 9530788, 10582370, 0, 0, 36768799, 40043785

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OFFSET

1,13

COMMENTS

The sequence enumerates a subset of the polyominoes enumerated by A144553.

LINKS

Table of n, a(n) for n=1..65.

FORMULA

For n multiple of 4, a(n) = A144553(n) - A234007(n/4); otherwise a(n) = A144553(n).

EXAMPLE

a(12)=1 because of:

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