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 A268769 Number of n X 3 0..2 arrays with some element plus some horizontally, vertically, diagonally or antidiagonally adjacent neighbor totalling two exactly once. 1
 12, 32, 112, 446, 1524, 5214, 17000, 54822, 173244, 541910, 1676448, 5146030, 15683076, 47518926, 143238872, 429867830, 1285009740, 3828046534, 11368576272, 33669165246, 99465517716, 293175780030, 862355454792, 2531766659654 (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) = 4*a(n-1) + 2*a(n-2) - 16*a(n-3) - a(n-4) + 12*a(n-5) - 4*a(n-6) for n>8. Empirical g.f.: 2*x*(6 - 8*x - 20*x^2 + 63*x^3 + 20*x^4 - 47*x^5 + 4*x^6 + 4*x^7) / (1 - 2*x - 3*x^2 + 2*x^3)^2. - Colin Barker, Jan 15 2019 EXAMPLE Some solutions for n=4: ..1..0..0. .1..0..0. .0..0..0. .1..2..1. .1..1..0. .2..2..2. .1..2..1 ..0..0..0. .1..0..0. .1..1..0. .1..2..2. .0..0..0. .1..2..2. .1..2..2 ..1..0..1. .0..0..0. .0..0..0. .2..2..1. .0..0..0. .2..2..1. .2..2..2 ..0..0..1. .1..0..0. .1..0..0. .1..2..2. .1..0..1. .2..1..2. .1..2..2 CROSSREFS Column 3 of A268774. Sequence in context: A143238 A102091 A303079 * A045669 A045660 A192213 Adjacent sequences:  A268766 A268767 A268768 * A268770 A268771 A268772 KEYWORD nonn AUTHOR R. H. Hardin, Feb 13 2016 STATUS approved

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Last modified January 17 15:12 EST 2020. Contains 330958 sequences. (Running on oeis4.)