A144057 - OEIS

A144057

Number of n X n binary arrays, symmetric about the diagonal and under 90-degree rotation, with every 1 adjacent to at least one other 1, but at most one 1 adjacent horizontally and at most one 1 adjacent vertically.

%I #5 Nov 25 2018 13:04:24

%S 1,2,1,3,5,13,23,83,158,743,1983,10973,39092,269179,1193276,10361962,

%T 58314051,622131402,4633595266,60891994633,582192966557,9528749362116,

%U 116024808662011,2351972316090989,37180717253935256,930816997530667262

%N Number of n X n binary arrays, symmetric about the diagonal and under 90-degree rotation, with every 1 adjacent to at least one other 1, but at most one 1 adjacent horizontally and at most one 1 adjacent vertically.

%K nonn

%O 1,2

%A _R. H. Hardin_, Sep 08 2008