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 A268967 Number of n X 4 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once. 1

%I

%S 60,912,11664,136080,1504656,16061328,167226768,1709114256,

%T 17218688400,171498136464,1692252695952,16569199473552,

%U 161173122151824,1559011041375120,15007175850454416,143849270956794768

%N Number of n X 4 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once.

%H R. H. Hardin, <a href="/A268967/b268967.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 18*a(n-1) - 81*a(n-2) for n>3.

%F Conjectures from _Colin Barker_, Jan 17 2019: (Start)

%F G.f.: 12*x*(1 - x)*(5 - 9*x) / (1 - 9*x)^2.

%F a(n) = 16*3^(2*n-3) * (8*n+3) for n>1.

%F (End)

%e Some solutions for n=4:

%e ..1..0..0..0. .1..0..1..2. .2..1..0..1. .2..1..2..1. .2..1..2..1

%e ..1..0..0..1. .0..0..1..2. .0..0..0..0. .2..1..2..2. .2..1..2..2

%e ..0..1..2..0. .1..0..2..2. .1..2..1..2. .2..2..1..2. .0..0..1..2

%e ..2..1..0..0. .0..1..2..1. .1..0..1..0. .1..0..1..1. .1..2..1..2

%Y Column 4 of A268971.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 16 2016

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Last modified August 17 22:43 EDT 2022. Contains 356195 sequences. (Running on oeis4.)