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A191552 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 2 diagonally or antidiagonally neighboring 1s 1
2, 8, 52, 528, 11275, 435987, 30448860, 3920809305, 920775496348, 394837552267029, 310020405028212730, 445022535834699088455, 1167728276848286755937076, 5603048100640429152817307256 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..24

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Sequence in context: A132228 A305004 A151879 * A154828 A349012 A057629

Adjacent sequences:  A191549 A191550 A191551 * A191553 A191554 A191555

KEYWORD

nonn

AUTHOR

R. H. Hardin Jun 05 2011

STATUS

approved

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Last modified November 29 21:32 EST 2021. Contains 349416 sequences. (Running on oeis4.)