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 A268624 Number of n X 4 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once. 1
 60, 666, 6300, 55452, 467190, 3819654, 30553014, 240364746, 1866503592, 14342680944, 109265781870, 826421076378, 6212333663082, 46453421706210, 345772280726172, 2563402622459652, 18936504080614278, 139446644995253358 (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) = 18*a(n-1) - 111*a(n-2) + 282*a(n-3) - 333*a(n-4) + 180*a(n-5) - 36*a(n-6) for n>7. Empirical g.f.: 6*x*(10 - 69*x + 162*x^2 - 157*x^3 + 87*x^4 - 36*x^5 + 8*x^6) / (1 - 9*x + 15*x^2 - 6*x^3)^2.- Colin Barker, Jan 14 2019 EXAMPLE Some solutions for n=4: ..1..2..2..2. .2..0..1..2. .2..2..2..2. .0..0..1..2. .2..1..0..1 ..0..1..2..1. .2..1..2..2. .1..2..2..2. .0..1..2..2. .2..2..1..0 ..1..2..1..0. .1..2..1..2. .2..2..2..2. .1..2..2..2. .2..1..0..1 ..0..1..0..1. .2..1..0..1. .1..1..2..1. .0..2..2..2. .1..2..1..2 CROSSREFS Column 4 of A268628. Sequence in context: A324068 A223242 A244837 * A088945 A269189 A136008 Adjacent sequences:  A268621 A268622 A268623 * A268625 A268626 A268627 KEYWORD nonn AUTHOR R. H. Hardin, Feb 09 2016 STATUS approved

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Last modified December 6 15:57 EST 2021. Contains 349565 sequences. (Running on oeis4.)