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 A231050 Number of 2 X n 0..3 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, no adjacent elements equal, and upper left element zero. 1
 0, 2, 14, 32, 100, 428, 1616, 5784, 21248, 78840, 290776, 1070552, 3946728, 14554440, 53657032, 197805128, 729249064, 2688543176, 9911794984, 36541580104, 134717359592, 496660701448, 1831031342376, 6750435204552, 24886729062376 (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) = 3*a(n-1) + 8*a(n-3) + 6*a(n-4) - 4*a(n-5) for n>6. Empirical g.f.: 2*x^2*(1 + x)*(1 + 3*x - 8*x^2 + 2*x^3) / (1 - 3*x - 8*x^3 - 6*x^4 + 4*x^5). - Colin Barker, Sep 26 2018 EXAMPLE Some solutions for n=4: ..0..3..0..3....0..3..2..3....0..1..2..3....0..3..0..3....0..3..2..3 ..2..1..2..1....0..1..0..1....2..3..0..3....0..1..2..1....2..1..0..1 CROSSREFS Row 2 of A231049. Sequence in context: A294558 A202638 A226565 * A337338 A322074 A083015 Adjacent sequences: A231047 A231048 A231049 * A231051 A231052 A231053 KEYWORD nonn AUTHOR R. H. Hardin, Nov 03 2013 STATUS approved

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Last modified February 2 05:15 EST 2023. Contains 359997 sequences. (Running on oeis4.)