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Number of n X n symmetric 0..1 arrays with each element equal to the product mod 2 of two of its horizontal and vertical neighbors.
1

%I #9 May 24 2024 13:31:16

%S 0,2,4,26,240,4063,110576,5046694,390350577,51445991632,

%T 11496127271424,4348804724288989,2784306483759192151,

%U 3019459887601073667024,5548682373331641079067391,17274304412990968236505863156

%N Number of n X n symmetric 0..1 arrays with each element equal to the product mod 2 of two of its horizontal and vertical neighbors.

%H R. H. Hardin, <a href="/A193480/b193480.txt">Table of n, a(n) for n = 1..19</a>

%e Some solutions for 4 X 4

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_, Jul 27 2011