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 A268621 Number of n X n 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totaling two no more than once. 1
 3, 42, 1086, 55452, 6000978, 1430057208, 767057092212, 938662461734076, 2643885168776274078, 17245474696462104041796, 261641272761781630830646332, 9262823664147270920479995625968, 767111588793900754143144516979246884 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Diagonal of A268628. LINKS R. H. Hardin, Table of n, a(n) for n = 1..14 EXAMPLE Some solutions for n=4 ..2..1..2..2. .0..0..0..0. .0..0..1..0. .2..1..0..0. .1..1..0..0 ..1..0..1..2. .0..1..1..0. .0..0..0..1. .1..0..0..0. .2..2..1..0 ..2..1..2..1. .1..0..0..1. .1..0..1..2. .0..1..0..0. .2..2..2..1 ..2..2..2..0. .0..0..1..0. .0..1..2..2. .0..0..0..1. .2..2..1..0 CROSSREFS Cf. A268628. Sequence in context: A206820 A157542 A078601 * A218308 A195010 A333323 Adjacent sequences:  A268618 A268619 A268620 * A268622 A268623 A268624 KEYWORD nonn AUTHOR R. H. Hardin, Feb 09 2016 STATUS approved

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Last modified January 28 12:35 EST 2022. Contains 350656 sequences. (Running on oeis4.)