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 A269030 Number of n X 3 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once. 1
 12, 48, 348, 2136, 12228, 67104, 357756, 1867560, 9593844, 48665904, 244357740, 1216672824, 6015296484, 29561944128, 144531868764, 703461546312, 3410368965588, 16475694411600, 79347347565132, 381071870841432 (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) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4) for n>5. Empirical g.f.: 12*x*(1 - 6*x + 18*x^2 - 16*x^3 + 4*x^4) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 18 2019 EXAMPLE Some solutions for n=4: ..1..2..2. .2..2..2. .1..0..2. .0..0..0. .2..2..1. .0..1..0. .2..1..0 ..2..2..2. .2..1..2. .1..2..1. .0..0..0. .1..2..2. .1..0..0. .0..1..2 ..2..1..0. .2..2..2. .2..2..1. .0..1..0. .2..2..1. .0..0..0. .0..1..0 ..2..1..0. .2..1..0. .2..2..1. .2..0..0. .2..1..2. .0..0..0. .0..0..2 CROSSREFS Column 3 of A269035. Sequence in context: A052601 A003498 A326743 * A222359 A002899 A222966 Adjacent sequences:  A269027 A269028 A269029 * A269031 A269032 A269033 KEYWORD nonn AUTHOR R. H. Hardin, Feb 18 2016 STATUS approved

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Last modified April 6 12:19 EDT 2020. Contains 333273 sequences. (Running on oeis4.)