A359520 - OEIS

%I #8 Jan 05 2023 11:04:38

%S 0,0,0,0,0,0,1,5,35,179,909,4285,19702,88040,386826,1674852,7174436,

%T 30462009

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

%F a(n) = A342537(n) - A000104(n) (simply connected polyominoes minus unholey polyominoes).

%e a(7) = 1 because of the holey heptomino.

%Y Cf. A000104, A000105, A001419, A342537, A359519.

%K nonn,more

%O 1,8

%A _John Mason_, Jan 04 2023