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 A278281 Number of 2 X n 0..1 arrays with every element both equal and not equal to some elements at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero. 1
 0, 2, 4, 13, 36, 109, 317, 938, 2754, 8114, 23869, 70264, 206775, 608587, 1791104, 5271458, 15514416, 45660689, 134384272, 395507653, 1164021849, 3425843074, 10082628314, 29674271654, 87334607025, 257035243772, 756482665279 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 2*a(n-1) + 3*a(n-2) - a(n-3) + a(n-4). Empirical g.f.: x^2*(2 - x^2) / (1 - 2*x - 3*x^2 + x^3 - x^4). - Colin Barker, Feb 09 2019 EXAMPLE Some solutions for n=4: ..0..1..1..0. .0..1..0..1. .0..0..0..0. .0..1..1..0. .0..1..1..0 ..0..1..1..0. .0..1..0..1. .1..1..1..1. .0..0..0..0. .0..0..1..0 CROSSREFS Row 2 of A278280. Sequence in context: A148236 A148237 A148238 * A148239 A148240 A151354 Adjacent sequences: A278278 A278279 A278280 * A278282 A278283 A278284 KEYWORD nonn AUTHOR R. H. Hardin, Nov 16 2016 STATUS approved

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Last modified December 7 07:48 EST 2023. Contains 367630 sequences. (Running on oeis4.)