%I #7 Apr 20 2020 00:03:11
%S 0,2,20,947,120815,58609226,86143630040,418568449327270,
%T 6527100767589040926,331808147283786972146018,
%U 54543586667142977292165721500,29084806316831133817614992597097070
%N Number of n X n 0..1 arrays with every element equal to 1, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero.
%C Diagonal of A301951.
%H R. H. Hardin, <a href="/A301945/b301945.txt">Table of n, a(n) for n = 1..13</a>
%e Some solutions for n=5
%e ..0..0..0..0..0. .0..0..0..1..1. .0..0..1..1..0. .0..0..0..1..1
%e ..0..1..0..1..1. .0..1..0..0..0. .0..1..1..0..0. .0..1..0..0..0
%e ..1..1..1..0..0. .1..0..1..1..0. .1..0..1..0..0. .1..1..1..0..0
%e ..1..0..0..0..1. .0..0..1..0..1. .0..1..1..1..1. .1..0..0..1..0
%e ..1..1..1..1..1. .0..1..0..1..1. .1..0..0..0..0. .0..1..1..0..0
%Y Cf. A301951.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 29 2018
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