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Number of free polyominoes of n cells with multiply-connected interiors.
2

%I #10 Jan 05 2023 11:04:42

%S 0,0,0,0,0,0,0,1,2,16,70,378,1772,8456,38623,174400,771944,3378937

%N Number of free polyominoes of n cells with multiply-connected interiors.

%F a(n) = A000105(n) - A342537(n) (all free polyominoes minus simply-connected interior polyominoes).

%e a(8) = 1 because of:

%e OOO

%e O O

%e OOO

%Y Cf. A000104, A000105, A001419, A342537, A359520.

%K nonn,more

%O 1,9

%A _John Mason_, Jan 04 2023