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A191604 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 5 horizontally, vertically or diagonally neighboring 1s 1

%I

%S 2,8,62,966,29888,1838552,224969616,54745613520,26495136860880,

%T 25502057625872912,48817512227401500592,185852155121293444267024,

%U 1407184656492293192061559200,21189763355834331020518358995456

%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 5 horizontally, vertically or diagonally neighboring 1s

%H R. H. Hardin, <a href="/A191604/b191604.txt">Table of n, a(n) for n = 1..21</a>

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,1

%A _R. H. Hardin_ Jun 08 2011

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Last modified June 22 04:06 EDT 2021. Contains 345367 sequences. (Running on oeis4.)