A191273 Number of n X n symmetric binary matrices with each 1 adjacent to exactly 1 diagonally or antidiagonally neighboring 1

1, 4, 9, 25, 168, 1360, 12423, 197679, 4404447, 124898323, 5318804048, 324994451931, 26856733887752, 3172635060583667, 535764786560787509, 125858757883842762915, 41716808217942795412293

Offset

1,2

Links

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

Example

Some solutions for n=4
..0..0..0..0....1..0..0..0....1..1..0..0....0..0..0..0....0..1..0..0
..0..1..0..0....0..1..1..0....1..1..0..0....0..0..1..0....1..0..0..0
..0..0..1..1....0..1..0..0....0..0..0..0....0..1..0..0....0..0..0..0
..0..0..1..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0

Crossrefs

Sequence in context: A025494 A087374 A081948 * A087361 A340642 A090117

Adjacent sequences: A191270 A191271 A191272 * A191274 A191275 A191276

Keyword

nonn

Author

R. H. Hardin May 29 2011

Status

approved