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.

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.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =0a(4) =1a(5) =0a(6) =3a(7) =0a(8) =4a(9) =1a(10) =10a(11) =3a(12) =17a(13) =6a(14) =35a(15) =15a(16) =64a(17) =31a(18) =128a(19) =74a(20) =241a(21) =145a(22) =476a(23) =332a(24) =912a(25) =649a(26) =1789a(27) =1446a(28) =3456a(29) =2821

External references