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%I #6 Dec 18 2015 18:17:40
%S 2,8,64,1024,31744,1966328,243334360,60208129728,29758502758208,
%T 29361656860572672,57846064835261224704,227511075000523635983456,
%U 1786387499611617848051648112,28002804481527546759736622292320
%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 7 knight-move neighboring 1s
%H R. H. Hardin, <a href="/A191575/b191575.txt">Table of n, a(n) for n = 1..16</a>
%e Some solutions for n=6
%e ..0..0..0..1..0..1....0..0..0..1..1..0....0..0..0..1..0..0....0..0..0..1..1..1
%e ..0..0..0..0..1..0....0..0..0..0..1..0....0..0..0..1..0..1....0..0..1..1..0..1
%e ..0..0..1..0..0..1....0..0..1..1..0..0....0..0..1..1..0..1....0..1..0..1..1..0
%e ..1..0..0..0..1..1....1..0..1..0..1..0....1..1..1..1..1..0....1..1..1..1..0..0
%e ..0..1..0..1..0..0....1..1..0..1..0..1....0..0..0..1..1..0....1..0..1..0..0..0
%e ..1..0..1..1..0..0....0..0..0..0..1..0....0..1..1..0..0..1....1..1..0..0..0..0
%K nonn
%O 1,1
%A _R. H. Hardin_ Jun 06 2011