A139007 Number of n X n symmetric binary matrices containing no more than two 1s in any 2 X 2 sub-block.

1, 2, 5, 25, 205, 2849, 66677, 2633485, 175143651, 19638725775, 3710411382331, 1181447019186469, 633957805831439213, 573281808520220290885, 873645764409736229092874, 2243689725607702437916265557

Offset

0,2

Links

R. H. Hardin, May 31 2008, Table of n, a(n) for n = 0..20

Crossrefs

Sequence in context: A324263 A049650 A191506 * A015486 A378327 A191951

Adjacent sequences: A139004 A139005 A139006 * A139008 A139009 A139010

Keyword

nonn

Author

R. H. Hardin, May 31 2008

Status

approved