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 A269146 Number of n X 2 0..3 arrays with some element plus some horizontally, antidiagonally or vertically adjacent neighbor totalling three exactly once. 1
 4, 80, 768, 6224, 46464, 330192, 2270592, 15251152, 100647168, 655139152, 4217820672, 26911075152, 170416738944, 1072338720464, 6710943646848, 41800542176720, 259288295447040, 1602497927690832, 9871915467776256 (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) = 12*a(n-1) - 38*a(n-2) + 12*a(n-3) - a(n-4) for n>5. Empirical g.f.: 4*x*(1 - x)*(1 + 9*x - x^2 - x^3) / (1 - 6*x + x^2)^2. - Colin Barker, Jan 19 2019 EXAMPLE Some solutions for n=4: ..3..2. .0..0. .2..0. .3..3. .1..0. .1..0. .1..3. .3..1. .0..2. .1..1 ..2..0. .2..3. .0..2. .3..3. .1..1. .0..2. .0..1. .1..0. .0..0. .3..3 ..1..0. .2..2. .0..3. .1..0. .1..3. .0..0. .0..0. .0..1. .2..3. .3..2 ..0..1. .3..3. .2..3. .0..0. .1..0. .1..3. .2..0. .0..2. .3..3. .0..2 CROSSREFS Column 2 of A269152. Sequence in context: A211152 A093854 A345459 * A192834 A054322 A114488 Adjacent sequences: A269143 A269144 A269145 * A269147 A269148 A269149 KEYWORD nonn AUTHOR R. H. Hardin, Feb 20 2016 STATUS approved

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Last modified February 4 19:58 EST 2023. Contains 360059 sequences. (Running on oeis4.)