A351190 Number of polyominoes of n cells with both horizontal and vertical symmetries, for which the 180-degree rotational symmetry has an axis that coincides with the center of a square, but without 90-degree rotational symmetry.

0, 0, 1, 0, 1, 0, 3, 0, 4, 1, 10, 3, 17, 6, 35, 15, 64, 31, 128, 74, 241, 145, 476, 332, 912, 649, 1789, 1446, 3456, 2821, 6779, 6164, 13161, 12049, 25839, 25981, 50348, 50844, 98957, 108514, 193375, 212766, 380522, 450568, 745248, 884843, 1468202, 1862065, 2880780, 3662652, 5681501, 7668922

Offset

1,7

Comments

This sequence enumerates a subset of the polyominoes enumerated by A056877.

Links

John Mason, Table of n, a(n) for n = 1..81

Formula

a(n) = A056877(n) - A346799(n/2) - A351191(n/4). - John Mason, Nov 18 2025

Example

a(3)=1 because of the straight tromino.

Crossrefs

Cf. A000105, A056877, A346799, A351191.

Sequence in context: A003815 A077140 A306562 * A131486 A127445 A324025

Adjacent sequences: A351187 A351188 A351189 * A351191 A351192 A351193

Keyword

nonn

Author

John Mason, Feb 04 2022

Extensions

More terms from John Mason, Mar 15 2023

Status

approved