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 A268623 Number of n X 3 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once. 1
 24, 174, 1086, 6300, 34890, 187224, 982086, 5063964, 25764066, 129678528, 646978302, 3204131172, 15769455258, 77195600520, 376136512950, 1825265294892, 8825528262738, 42536536932432, 204425809550958, 979908028544244 (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) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4). Empirical g.f.: 6*x*(4 - 11*x + 7*x^2 + x^3) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 14 2019 EXAMPLE Some solutions for n=6: ..0..0..1. .0..0..0. .2..2..1. .1..0..1. .1..2..1. .1..0..1. .1..0..1 ..0..1..2. .1..0..0. .0..1..2. .0..0..0. .0..1..2. .0..1..2. .0..0..0 ..2..2..2. .0..1..0. .1..0..1. .1..0..0. .0..0..1. .1..0..1. .1..1..0 ..1..2..2. .1..2..1. .0..1..0. .0..0..1. .1..0..0. .2..1..0. .0..0..0 ..2..1..2. .0..1..0. .1..0..1. .2..1..0. .2..2..1. .2..0..1. .1..0..0 ..1..2..2. .0..1..0. .0..1..2. .1..0..1. .1..2..2. .2..1..2. .2..1..0 CROSSREFS Column 3 of A268628. Sequence in context: A221069 A272125 A166756 * A209716 A209709 A209986 Adjacent sequences:  A268620 A268621 A268622 * A268624 A268625 A268626 KEYWORD nonn AUTHOR R. H. Hardin, Feb 09 2016 STATUS approved

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Last modified January 24 21:49 EST 2022. Contains 350565 sequences. (Running on oeis4.)