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 A268792 Number of n X 2 0..2 arrays with some element plus some horizontally, vertically or antidiagonally adjacent neighbor totalling two exactly once. 1
 3, 22, 78, 234, 652, 1714, 4360, 10820, 26366, 63346, 150482, 354196, 827310, 1919884, 4430664, 10175910, 23272918, 53029498, 120435100, 272714858, 615904208, 1387638220, 3119557838, 6999162874, 15675003042, 35046218020 (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) = 2*a(n-1) + 3*a(n-2) - 2*a(n-3) - 6*a(n-4) - 4*a(n-5) - a(n-6) for n>7. Empirical g.f.: x*(3 + 16*x + 25*x^2 + 18*x^3 + 12*x^4 + 8*x^5 + 3*x^6) / (1 - x - 2*x^2 - x^3)^2. - Colin Barker, Jan 15 2019 EXAMPLE Some solutions for n=4: ..2..1. .0..0. .1..2. .0..0. .0..2. .2..2. .2..0. .0..0. .0..1. .1..2 ..0..0. .1..1. .2..1. .0..1. .1..2. .1..2. .1..0. .0..1. .0..0. .2..2 ..0..0. .0..0. .1..0. .2..2. .2..2. .2..2. .0..0. .0..0. .0..1. .2..1 ..0..0. .0..0. .0..1. .2..1. .2..1. .1..1. .0..1. .1..2. .1..0. .2..1 CROSSREFS Column 2 of A268798. Sequence in context: A178492 A005288 A143166 * A055550 A075204 A106150 Adjacent sequences:  A268789 A268790 A268791 * A268793 A268794 A268795 KEYWORD nonn AUTHOR R. H. Hardin, Feb 13 2016 STATUS approved

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)