A351190 - cp's OEIS frontend

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.

%I A351190 #14 Mar 15 2023 10:54:57
%S A351190 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,
%T A351190 649,1789,1446,3456,2821,6779,6164,13161,12049,25839,25981,50348,
%U A351190 50844,98957,108514,193375,212766,380522,450568,745248,884843,1468202,1862065,2880780,3662652,5681501,7668922
%N 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.
%C A351190 This sequence enumerates a subset of the polyominoes enumerated by A056877.
%e A351190 a(3)=1 because of the straight tromino.
%Y A351190 Cf. A000105, A056877.
%K A351190 nonn
%O A351190 1,7
%A A351190 _John Mason_, Feb 04 2022
%E A351190 More terms from _John Mason_, Mar 15 2023

cp's OEIS Frontend

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.