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%I #7 Feb 26 2019 12:06:09
%S 4,23,117,609,3159,16389,85041,441225,2289339,11878281,61631001,
%T 319774761,1659164103,8608637997,44666257401,231752633913,
%U 1202457662523,6238998904833,32371291359585,167959719216009,871465613342823
%N Number of n X 3 0..1 arrays with every 1 horizontally or antidiagonally adjacent to 1 or 2 neighboring 1s.
%H R. H. Hardin, <a href="/A297309/b297309.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) + 11*a(n-2) + 3*a(n-3) - 6*a(n-4).
%F Empirical g.f.: x*(4 + 11*x + 4*x^2 - 7*x^3) / (1 - 3*x - 11*x^2 - 3*x^3 + 6*x^4). - _Colin Barker_, Feb 26 2019
%e Some solutions for n=5:
%e ..1..1..1. .0..1..0. .1..1..0. .0..1..0. .1..1..0. .0..0..0. .1..1..0
%e ..0..1..0. .1..0..0. .1..1..1. .1..0..1. .1..1..0. .0..0..0. .1..1..1
%e ..1..0..0. .1..1..1. .0..0..0. .0..1..0. .1..0..1. .0..0..0. .0..0..0
%e ..0..0..1. .0..1..0. .1..1..1. .1..1..0. .0..1..0. .1..1..0. .0..1..0
%e ..1..1..0. .0..1..1. .0..1..1. .0..0..0. .0..1..1. .1..1..1. .1..1..1
%Y Column 3 of A297314.
%K nonn
%O 1,1
%A _R. H. Hardin_, Dec 28 2017
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