cp's OEIS Frontend

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.

%I A351160 #18 Dec 20 2024 12:57:57
%S A351160 0,0,0,1,1,2,4,10,14,37,55,142,208,531,792,2015,3029,7621
%N 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.
%C A351160 This sequence enumerates a subset of the polyominoes enumerated by A056878.
%F A351160 a(n) = A056878(2*n) - A351159(2*n).
%e A351160 a(4)=1 because of:
%e A351160     O
%e A351160    OOO
%e A351160   OOO
%e A351160    O
%Y A351160 Cf. A000105, A056878, A351159.
%K A351160 nonn,more
%O A351160 1,6
%A A351160 _John Mason_, Feb 03 2022
%E A351160 a(17)-a(18) from _John Mason_, Dec 17 2024