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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
 60, 912, 11664, 136080, 1504656, 16061328, 167226768, 1709114256, 17218688400, 171498136464, 1692252695952, 16569199473552, 161173122151824, 1559011041375120, 15007175850454416, 143849270956794768 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 18*a(n-1) - 81*a(n-2) for n>3. Conjectures from Colin Barker, Jan 17 2019: (Start) G.f.: 12*x*(1 - x)*(5 - 9*x) / (1 - 9*x)^2. a(n) = 16*3^(2*n-3) * (8*n+3) for n>1. (End) EXAMPLE Some solutions for n=4: ..1..0..0..0. .1..0..1..2. .2..1..0..1. .2..1..2..1. .2..1..2..1 ..1..0..0..1. .0..0..1..2. .0..0..0..0. .2..1..2..2. .2..1..2..2 ..0..1..2..0. .1..0..2..2. .1..2..1..2. .2..2..1..2. .0..0..1..2 ..2..1..0..0. .0..1..2..1. .1..0..1..0. .1..0..1..1. .1..2..1..2 CROSSREFS Column 4 of A268971. Sequence in context: A305625 A056321 A056312 * A189607 A223213 A271651 Adjacent sequences:  A268964 A268965 A268966 * A268968 A268969 A268970 KEYWORD nonn AUTHOR R. H. Hardin, Feb 16 2016 STATUS approved

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Last modified June 28 10:20 EDT 2022. Contains 354903 sequences. (Running on oeis4.)