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 A268973 Number of 3 X n 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once. 1
 27, 336, 2016, 11664, 63792, 339480, 1770048, 9084744, 46050480, 231090264, 1150053408, 5683587048, 27921925008, 136471932792, 664055030016, 3218568401160, 15545839096944, 74855120204952, 359437016141280 (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) for n>6. Empirical g.f.: 3*x*(9 + 22*x - 187*x^2 + 236*x^3 - 332*x^4 + 280*x^5) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 17 2019 EXAMPLE Some solutions for n=4: ..1..2..1..0. .2..2..2..2. .1..2..2..2. .2..1..2..2. .0..1..2..2 ..1..2..0..1. .2..2..1..0. .1..2..2..1. .0..0..1..2. .0..1..2..1 ..1..0..0..0. .1..2..1..2. .0..1..0..0. .1..2..1..0. .0..1..2..1 CROSSREFS Row 3 of A268971. Sequence in context: A022719 A290405 A048709 * A160223 A182668 A076394 Adjacent sequences:  A268970 A268971 A268972 * A268974 A268975 A268976 KEYWORD nonn AUTHOR R. H. Hardin, Feb 16 2016 STATUS approved

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Last modified June 25 22:13 EDT 2022. Contains 354868 sequences. (Running on oeis4.)