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A268624 Number of n X 4 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.

%I A268624 #8 Jan 14 2019 09:01:34
%S A268624 60,666,6300,55452,467190,3819654,30553014,240364746,1866503592,
%T A268624 14342680944,109265781870,826421076378,6212333663082,46453421706210,
%U A268624 345772280726172,2563402622459652,18936504080614278,139446644995253358
%N A268624 Number of n X 4 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.
%H A268624 R. H. Hardin, <a href="/A268624/b268624.txt">Table of n, a(n) for n = 1..210</a>
%F A268624 Empirical: a(n) = 18*a(n-1) - 111*a(n-2) + 282*a(n-3) - 333*a(n-4) + 180*a(n-5) - 36*a(n-6) for n>7.
%F A268624 Empirical g.f.: 6*x*(10 - 69*x + 162*x^2 - 157*x^3 + 87*x^4 - 36*x^5 + 8*x^6) / (1 - 9*x + 15*x^2 - 6*x^3)^2.- _Colin Barker_, Jan 14 2019
%e A268624 Some solutions for n=4:
%e A268624 ..1..2..2..2. .2..0..1..2. .2..2..2..2. .0..0..1..2. .2..1..0..1
%e A268624 ..0..1..2..1. .2..1..2..2. .1..2..2..2. .0..1..2..2. .2..2..1..0
%e A268624 ..1..2..1..0. .1..2..1..2. .2..2..2..2. .1..2..2..2. .2..1..0..1
%e A268624 ..0..1..0..1. .2..1..0..1. .1..1..2..1. .0..2..2..2. .1..2..1..2
%Y A268624 Column 4 of A268628.
%K A268624 nonn
%O A268624 1,1
%A A268624 _R. H. Hardin_, Feb 09 2016