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%I #7 Apr 20 2020 00:02:15
%S 0,2,4,68,1197,31061,2341241,221373169,47059520355,17662862033686,
%T 11449618914826511,15088557751754929900,33289512591289837483184,
%U 143748055903459113756507351,1108648718940092116466729395935
%N Number of n X n 0..1 arrays with every element equal to 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero.
%C Diagonal of A301823.
%H R. H. Hardin, <a href="/A301818/b301818.txt">Table of n, a(n) for n = 1..16</a>
%e Some solutions for n=5
%e ..0..0..1..1..0. .0..0..0..1..1. .0..0..1..1..1. .0..0..0..1..1
%e ..0..1..1..0..0. .1..1..0..0..1. .0..1..0..0..1. .1..1..0..0..0
%e ..0..0..1..1..1. .1..1..0..1..1. .1..1..0..1..0. .1..1..1..1..1
%e ..0..1..0..1..1. .1..0..0..0..0. .1..0..1..0..1. .0..0..0..0..0
%e ..1..0..0..1..1. .1..1..1..0..0. .1..1..0..1..1. .1..1..1..1..1
%Y Cf. A301823.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 27 2018
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