|
%I #6 Dec 18 2015 18:17:39
%S 2,8,60,855,24282,1352976,146740728,31117674297,12907153049676,
%T 10462960655266920,16578587764555196630,51351429814865700365643,
%U 310919919699021477652128426,3679876610343227082947024870052
%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 3 diagonally or antidiagonally neighboring 1s
%H R. H. Hardin, <a href="/A191553/b191553.txt">Table of n, a(n) for n = 1..23</a>
%e Some solutions for n=4
%e ..0..1..0..1....1..1..1..0....0..0..0..1....1..0..1..0....1..0..1..0
%e ..1..0..0..1....1..0..0..1....0..1..1..0....0..1..0..1....0..1..0..1
%e ..0..0..0..0....1..0..0..1....0..1..0..0....1..0..0..0....1..0..0..0
%e ..1..1..0..1....0..1..1..0....1..0..0..1....0..1..0..0....0..1..0..1
%K nonn
%O 1,1
%A _R. H. Hardin_ Jun 05 2011
| 