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.

1, 2, 1, 3, 5, 13, 23, 83, 158, 743, 1983, 10973, 39092, 269179, 1193276, 10361962, 58314051, 622131402, 4633595266, 60891994633, 582192966557, 9528749362116, 116024808662011, 2351972316090989, 37180717253935256, 930816997530667262

Offset

1,2

Links

Table of n, a(n) for n=1..26.

Crossrefs

Sequence in context: A092944 A049902 A096631 * A272891 A219274 A241498

Adjacent sequences: A144054 A144055 A144056 * A144058 A144059 A144060

Keyword

nonn

Author

R. H. Hardin, Sep 08 2008

Status

approved