A351160 Number of polyominoes of 2n cells with both diagonal symmetries, for which the 180-degree rotational symmetry has an axis that coincides with a vertex of a square, but without 90-degree rotational symmetry.

0, 0, 0, 1, 1, 2, 4, 10, 14, 37, 55, 142, 208, 531, 792, 2015, 3029, 7621

Offset: 1

Author

John Mason, Feb 03 2022

Keywords

• nonn
• more

Comments

This sequence enumerates a subset of the polyominoes enumerated by A056878.

Examples

			a(4)=1 because of:
    O
   OOO
  OOO
   O
		

Crossrefs

Cf. A000105, A056878, A351159.

Formula

a(n) = A056878(2*n) - A351159(2*n).

Extensions

a(17)-a(18) from John Mason, Dec 17 2024