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%I #7 Apr 19 2020 23:44:04
%S 3,34,332,5848,195384,12432856,1508087180,348686105792,
%T 154172619407288,130573457756588328,212323461305457440492,
%U 663970589813116610557692,3999438097971983178736358520,46462227980008803491191644654968
%N Number of n X n 0..2 arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two not more than once.
%C Diagonal of A268809.
%H R. H. Hardin, <a href="/A268802/b268802.txt">Table of n, a(n) for n = 1..18</a>
%e Some solutions for n=4
%e ..2..2..2..2. .0..0..1..2. .2..1..0..0. .0..1..0..0. .1..2..2..1
%e ..1..1..2..2. .1..2..2..2. .2..0..0..0. .1..0..0..0. .2..2..2..2
%e ..2..2..2..2. .2..2..1..2. .1..0..0..1. .0..0..0..1. .1..2..2..1
%e ..1..2..1..2. .2..2..2..2. .0..0..0..0. .0..0..0..0. .2..1..2..1
%Y Cf. A268809.
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 13 2016
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