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%I #8 Jan 19 2019 06:42:18
%S 60,1740,40908,872460,17593092,342055548,6482020140,120520189980,
%T 2208175854948,39988864047276,717328864510092,12766536225007020,
%U 225704408971133124,3967699804321484124,69407066832964073964
%N Number of n X 3 0..3 arrays with some element plus some horizontally or vertically adjacent neighbor totalling three no more than once.
%H R. H. Hardin, <a href="/A269104/b269104.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 36*a(n-1) - 378*a(n-2) + 972*a(n-3) - 729*a(n-4) for n>5.
%F Empirical g.f.: 12*x*(5 - 35*x + 79*x^2 - 69*x^3 + 18*x^4) / (1 - 18*x + 27*x^2)^2. - _Colin Barker_, Jan 19 2019
%e Some solutions for n=3:
%e ..1..0..2. .0..0..2. .2..3..3. .3..3..2. .2..2..3. .1..1..1. .2..3..3
%e ..1..1..0. .0..1..3. .0..2..3. .3..2..0. .2..3..3. .0..0..0. .2..2..3
%e ..3..2..2. .2..0..2. .0..0..0. .3..0..1. .1..3..3. .1..1..0. .0..0..3
%Y Column 3 of A269109.
%K nonn
%O 1,1
%A _R. H. Hardin_, Feb 19 2016
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