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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

%I

%S 2,8,52,528,11275,435987,30448860,3920809305,920775496348,

%T 394837552267029,310020405028212730,445022535834699088455,

%U 1167728276848286755937076,5603048100640429152817307256

%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 2 diagonally or antidiagonally neighboring 1s

%H R. H. Hardin, <a href="/A191552/b191552.txt">Table of n, a(n) for n = 1..24</a>

%e Some solutions for n=4

%e ..1..1..0..0....0..0..0..1....1..1..0..0....0..0..0..0....1..0..1..0

%e ..1..1..1..0....0..0..0..1....1..1..1..0....0..0..1..0....0..0..1..0

%e ..0..1..0..0....0..0..1..0....0..1..1..0....0..1..1..1....1..1..1..1

%e ..0..0..0..1....1..1..0..0....0..0..0..0....0..0..1..1....0..0..1..1

%K nonn

%O 1,1

%A _R. H. Hardin_ Jun 05 2011

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Last modified January 28 18:56 EST 2022. Contains 350657 sequences. (Running on oeis4.)