A140417 Half the number of n X n symmetric binary matrices with each 1 adjacent to some 0 horizontally (and vertically) and each 0 adjacent to some 1 horizontally (and vertically).

1, 1, 4, 13, 77, 556, 5859, 83423, 1659982, 45479269, 1727097809, 90646136576, 6583459833641, 661303481127357, 91895146207819652, 17663776192483786871

Offset

2,3

Links

Table of n, a(n) for n=2..17.

Crossrefs

Sequence in context: A012075 A197942 A337286 * A301396 A221512 A061143

Adjacent sequences: A140414 A140415 A140416 * A140418 A140419 A140420

Keyword

nonn

Author

R. H. Hardin, Jun 17 2008

Status

approved