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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.
1

%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