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 A268906 Number of 3 X n 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. 1
 0, 240, 1584, 9720, 54936, 299088, 1585800, 8244288, 42216696, 213602256, 1070280936, 5319700704, 26262038232, 128900271600, 629516497608, 3061019061504, 14827169463480, 71576870716944, 344483107968168 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 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) for n>6. Empirical g.f.: 24*x^2*(10 - 34*x + 35*x^2 - 47*x^3 + 37*x^4) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 16 2019 EXAMPLE Some solutions for n=4: ..1..0..0..2. .1..1..2..2. .0..1..0..1. .0..2..2..2. .0..1..2..2 ..0..1..2..2. .2..2..1..2. .2..1..2..1. .1..2..2..2. .2..1..0..1 ..2..1..2..1. .1..2..2..1. .2..2..0..0. .1..2..2..1. .0..1..0..0 CROSSREFS Row 3 of A268904. Sequence in context: A235205 A233878 A157766 * A234763 A268796 A290655 Adjacent sequences: A268903 A268904 A268905 * A268907 A268908 A268909 KEYWORD nonn AUTHOR R. H. Hardin, Feb 15 2016 STATUS approved

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Last modified December 8 14:17 EST 2022. Contains 358693 sequences. (Running on oeis4.)