A362709 - cp's OEIS frontend

A362709 a(n) is the number of almost almost unitary polyominoes of size n. An almost almost unitary polyomino is one in which all but 2 of its perimeter walls have length 1.

%I A362709 #11 May 01 2023 10:01:42
%S A362709 0,1,2,2,4,12,15,29,58,116,199,403,790,1509,2857,5700,10941,21032
%N A362709 a(n) is the number of almost almost unitary polyominoes of size n. An almost almost unitary polyomino is one in which all but 2 of its perimeter walls have length 1.
%H A362709 George Sicherman, <a href="https://sicherman.net/nunitary/nunitaryaa.html">Catalogue of Almost Almost Unitary Polyominoes</a>
%e A362709 a(4)=2 because of:
%e A362709   O  O
%e A362709   O  OO
%e A362709   O   O
%e A362709   O
%Y A362709 Cf. A245660, A362708.
%K A362709 nonn,hard,more
%O A362709 1,3
%A A362709 _John Mason_, Apr 30 2023

cp's OEIS Frontend

A362709 a(n) is the number of almost almost unitary polyominoes of size n. An almost almost unitary polyomino is one in which all but 2 of its perimeter walls have length 1.