%I #6 Sep 21 2018 21:48:05
%S 1,2,3,7,16,43,117,330,935,2667,7616,21775,62273,178130,509563,
%T 1457727,4170224,11930147,34129757,97638522,279324735,799093699,
%U 2286051744,6539949991,18709526921,53524323778,153122698291,438054310967
%N Number of n X 3 0..1 arrays with every element equal to 0, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero.
%H R. H. Hardin, <a href="/A301902/b301902.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) +a(n-2) -4*a(n-3).
%e Some solutions for n=5
%e ..0..1..1. .0..1..0. .0..1..1. .0..1..1. .0..1..1. .0..1..1. .0..1..0
%e ..1..1..0. .0..1..1. .1..1..0. .1..1..1. .1..1..0. .1..1..1. .0..1..0
%e ..1..1..1. .1..1..1. .1..1..0. .0..1..1. .0..1..0. .0..1..1. .0..1..0
%e ..0..1..1. .0..1..1. .1..1..1. .0..1..1. .0..1..1. .1..1..0. .0..1..0
%e ..1..1..0. .1..1..0. .1..1..0. .1..1..0. .1..1..0. .0..1..0. .0..1..0
%Y Column 3 of A301906.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 28 2018