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 A268966 Number of n X 3 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once. 1
 24, 240, 2016, 15552, 114048, 808704, 5598720, 38071296, 255301632, 1693052928, 11125776384, 72559411200, 470184984576, 3030081011712, 19434312695808, 124128835928064, 789910774087680, 5010291195641856, 31686706480545792 (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) = 12*a(n-1) - 36*a(n-2). Conjectures from Colin Barker, Jan 17 2019: (Start) G.f.: 24*x*(1 - 2*x) / (1 - 6*x)^2. a(n) = 2^(n+2) * 3^(n-1) * (2*n+1). (End) EXAMPLE Some solutions for n=4: ..1..0..0. .0..1..2. .0..2..2. .2..2..2. .0..0..0. .1..2..1. .1..2..2 ..1..1..2. .2..2..2. .1..2..2. .1..2..2. .0..1..0. .2..1..0. .0..1..0 ..2..2..2. .1..2..2. .2..2..2. .1..0..1. .2..0..1. .0..0..1. .0..0..1 ..2..2..2. .2..1..0. .2..2..2. .1..0..0. .1..0..1. .1..2..1. .0..0..0 CROSSREFS Column 3 of A268971. Sequence in context: A000919 A353665 A353775 * A014340 A052753 A353358 Adjacent sequences:  A268963 A268964 A268965 * A268967 A268968 A268969 KEYWORD nonn AUTHOR R. H. Hardin, Feb 16 2016 STATUS approved

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Last modified August 8 21:07 EDT 2022. Contains 356016 sequences. (Running on oeis4.)