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%I #9 Oct 10 2022 20:12:23
%S 0,0,0,0,0,0,0,1,0,0,0,2,2,0,0,7,7,0,0,22,24,0,0,71,82,0,0,239,280,0,
%T 0,817,970,0,0,2841,3403,0,0,10027,12064,0,0,35800,43193,0,0,129007,
%U 156011,0,0,468541,567664,0,0,1713174
%N a(n) is the number of free unholey polyominoes of n cells with 90-degree rotational symmetry and no other.
%Y Cf. A000104, A144553.
%K nonn
%O 1,12
%A _John Mason_, Oct 10 2022