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A191223 Number of n X n symmetric binary matrices with each 1 adjacent to exactly 2 king-move neighboring 1s 1
1, 3, 6, 16, 88, 534, 4001, 49783, 802282, 16846980, 518093110, 21604679482, 1210757513851, 95028176738441, 10229389014494032, 1500221649654979714, 303756994018728446946, 84493641616490831589232 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..20

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A051271 A028405 A328276 * A301515 A014645 A195996

Adjacent sequences:  A191220 A191221 A191222 * A191224 A191225 A191226

KEYWORD

nonn

AUTHOR

R. H. Hardin May 27 2011

STATUS

approved

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Last modified December 4 10:44 EST 2021. Contains 349486 sequences. (Running on oeis4.)