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%I #12 Feb 05 2022 03:11:08
%S 0,0,0,0,0,0,1,0,0,0,2,1,3,1,6,4,9,6,20,19,32,25,64,82,114,107,217,
%T 332,397,442,751,1316
%N Number of polyominoes of n cells with both diagonal 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 This sequence enumerates a subset of the polyominoes enumerated by A056878.
%F For odd n, a(n) = A056878(n); for even n, a(n) = A056878(n) - A351160(n/2).
%e For a(7)=1, the heptomino with exactly fourfold symmetry and axes of symmetry parallel to the diagonals of the cells is composed of two 2 X 2 squares with one cell in common.
%Y Cf. A000105, A056878, A351160.
%K nonn,more
%O 1,11
%A _John Mason_, Feb 03 2022
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