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 A201347 Number of n X 2 0..1 arrays with rows and columns lexicographically nondecreasing and every element equal to at least one horizontal or vertical neighbor. 1
 2, 4, 8, 14, 23, 36, 54, 78, 109, 148, 196, 254, 323, 404, 498, 606, 729, 868, 1024, 1198, 1391, 1604, 1838, 2094, 2373, 2676, 3004, 3358, 3739, 4148, 4586, 5054, 5553, 6084, 6648, 7246, 7879, 8548, 9254, 9998, 10781, 11604, 12468, 13374, 14323, 15316, 16354 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 2 of A201353. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = (1/6)*n^3 - (1/2)*n^2 + (10/3)*n - 2 for n>1. Conjectures from Colin Barker, May 22 2018: (Start) G.f.: x*(2 - 4*x + 4*x^2 - 2*x^3 + x^4) / (1 - x)^4. a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>5. (End) EXAMPLE Some solutions for n=10: ..0..0....0..0....0..0....0..0....0..1....0..1....0..0....0..0....0..0....0..0 ..0..0....0..0....0..0....0..0....0..1....0..1....0..0....0..1....0..1....0..0 ..0..1....0..0....0..0....0..0....1..0....0..1....0..0....0..1....0..1....0..0 ..0..1....0..0....1..1....0..1....1..0....0..1....0..0....0..1....0..1....0..0 ..0..1....0..0....1..1....0..1....1..0....0..1....0..0....1..0....1..0....0..0 ..0..1....0..0....1..1....0..1....1..0....1..0....0..0....1..0....1..0....0..1 ..0..1....0..0....1..1....1..1....1..0....1..0....0..1....1..0....1..0....0..1 ..0..1....0..0....1..1....1..1....1..0....1..0....0..1....1..1....1..0....0..1 ..1..0....0..1....1..1....1..1....1..1....1..0....0..1....1..1....1..0....1..0 ..1..0....1..1....1..1....1..1....1..1....1..0....1..1....1..1....1..1....1..0 CROSSREFS Cf. A201353. Sequence in context: A261968 A138526 A286522 * A089054 A055291 A091773 Adjacent sequences:  A201344 A201345 A201346 * A201348 A201349 A201350 KEYWORD nonn AUTHOR R. H. Hardin, Nov 30 2011 STATUS approved

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Last modified October 22 00:52 EDT 2019. Contains 328315 sequences. (Running on oeis4.)