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A191274 Number of n X n symmetric binary matrices with each 1 adjacent to exactly 2 diagonally or antidiagonally neighboring 1s 1
1, 1, 2, 3, 8, 35, 208, 1147, 10098, 106904, 1615656, 31267328, 833655362, 29769092579, 1422289731681, 88322500448612, 7254260374065120, 782791757341222545, 111845565903325791194, 21080332457396845047136 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..22

EXAMPLE

All solutions for n=4

..0..0..0..0....0..1..0..0....0..0..0..0

..0..0..1..0....1..0..1..0....0..0..0..0

..0..1..0..1....0..1..0..0....0..0..0..0

..0..0..1..0....0..0..0..0....0..0..0..0

CROSSREFS

Sequence in context: A005370 A112866 A041657 * A041789 A174899 A201370

Adjacent sequences:  A191271 A191272 A191273 * A191275 A191276 A191277

KEYWORD

nonn

AUTHOR

R. H. Hardin May 29 2011

STATUS

approved

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Last modified February 17 12:32 EST 2020. Contains 331996 sequences. (Running on oeis4.)