A351191 Number of polyominoes of 4n cells with both horizontal and vertical symmetries, for which the 180-degree rotational symmetry has an axis that coincides with a vertex of a square of the underlying matrix, but without 90-degree rotational symmetry.

0, 1, 2, 9, 29, 106, 372, 1356, 4928, 18200, 67541, 252847, 951615, 3602131, 13696141, 52295335, 200393559, 770406039, 2970353199, 11482373919, 44491696182, 172766226170, 672185941552, 2619994156474, 10228900153083, 39996337310835, 156612012801698

Offset

1,3

Comments

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

Links

John Mason, Table of n, a(n) for n = 1..50

Formula

a(n)=A144553(n) + A056877(n) + 2 * A006747(n) + 2 * A006746(n) + 4 * A006749(n) + A006748(n).

Example

a(2)=1 because of the 2 by 4 octomino.

Crossrefs

Cf. A000105, A056877, A144553, A006747, A006746, A006749, A006748.

Sequence in context: A152891 A181545 A069006 * A241774 A183383 A280853

Adjacent sequences: A351188 A351189 A351190 * A351192 A351193 A351194

Keyword

nonn

Author

John Mason, Feb 05 2022

Status

approved