A191479 - OEIS

%I #6 Dec 18 2015 18:17:39

%S 2,8,42,445,8336,273578,16060725,1663317205,304789975903,

%T 99026690954574,56934478978072688,57952230532394115913,

%U 104449989219446543530778,333288010626782017792094457,1882901103468898454919475637369

%N Number of n X n symmetric binary matrices with each 1 adjacent to no more than 3 king-move neighboring 1s

%H R. H. Hardin, <a href="/A191479/b191479.txt">Table of n, a(n) for n = 1..17</a>

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,1

%A _R. H. Hardin_ Jun 03 2011