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 A269761 Number of n X 2 0..5 arrays with some element plus some horizontally or vertically adjacent neighbor totalling five exactly once. 1
 6, 480, 17520, 524160, 14288400, 368958240, 9195061680, 223482006720, 5331222081360, 125355762453600, 2913873085171440, 67100778335162880, 1533214659516235920, 34803572453875078560, 785602378216093258800 (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) = 42*a(n-1) - 441*a(n-2) for n>3. Conjectures from Colin Barker, Jan 28 2019: (Start) G.f.: 6*x*(1 + 38*x + x^2) / (1 - 21*x)^2. a(n) = 80 * 3^(n-2) * 7^(n-3) * (31*n-20) for n>1. (End) EXAMPLE Some solutions for n=3: ..5..3. .4..0. .0..4. .0..4. .2..3. .5..4. .0..3. .2..5. .4..4. .4..4 ..1..4. .1..0. .0..3. .0..5. .5..5. .2..1. .1..4. .4..2. .2..5. .1..2 ..3..0. .0..4. .5..3. .4..5. .1..5. .0..0. .5..5. .4..1. .0..0. .2..4 CROSSREFS Column 2 of A269767. Sequence in context: A220865 A080295 A084108 * A229503 A318634 A006713 Adjacent sequences:  A269758 A269759 A269760 * A269762 A269763 A269764 KEYWORD nonn AUTHOR R. H. Hardin, Mar 04 2016 STATUS approved

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Last modified November 26 15:51 EST 2020. Contains 338640 sequences. (Running on oeis4.)