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 A280279 Number of n X 1 0..2 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards. 5
 0, 0, 1, 2, 8, 28, 94, 304, 960, 2976, 9096, 27488, 82304, 244544, 721888, 2119168, 6191104, 18011136, 52203648, 150809088, 434382848, 1247857664, 3576143360, 10226274304, 29184704512, 83138240512, 236438194176, 671370043392 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Column 1 of A280284. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4) for n>7. Empirical g.f.: x^3*(1 - 2*x + 4*x^3 + 2*x^4) / (1 - 2*x - 2*x^2)^2. - Colin Barker, Feb 19 2018 EXAMPLE All solutions for n=4: ..0. .0 ..1. .0 ..1. .0 ..1. .1 CROSSREFS Cf. A280284. Sequence in context: A178222 A090426 A279193 * A060995 A106731 A318010 Adjacent sequences: A280276 A280277 A280278 * A280280 A280281 A280282 KEYWORD nonn AUTHOR R. H. Hardin, Dec 30 2016 STATUS approved

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Last modified September 23 16:34 EDT 2023. Contains 365554 sequences. (Running on oeis4.)