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 A227085 Number of n X 2 binary arrays indicating whether each 2 X 2 subblock of a larger binary array has lexicographically increasing rows and columns, for some larger (n+1) X 3 binary array with rows and columns of the latter in lexicographically nondecreasing order. 1
 4, 12, 29, 62, 122, 225, 393, 655, 1048, 1618, 2421, 3524, 5006, 6959, 9489, 12717, 16780, 21832, 28045, 35610, 44738, 55661, 68633, 83931, 101856, 122734, 146917, 174784, 206742, 243227, 284705, 331673, 384660, 444228, 510973, 585526, 668554 (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) = (1/120)*n^5 + (1/24)*n^4 + (5/24)*n^3 + (35/24)*n^2 + (77/60)*n + 1. Conjectures from Colin Barker, Sep 07 2018: (Start) G.f.: x*(2 - x)*(2 - 5*x + 6*x^2 - 3*x^3 + x^4) / (1 - x)^6. a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6. (End) EXAMPLE Some solutions for n=4: ..0..0....1..1....1..0....1..1....0..0....0..0....1..0....0..0....1..0....1..0 ..0..0....1..0....0..1....1..0....0..0....0..0....1..0....0..1....0..0....0..0 ..0..1....0..0....0..0....0..0....0..0....0..1....0..0....0..1....0..0....0..1 ..1..1....0..1....0..1....0..0....0..1....0..1....0..0....0..0....0..0....0..0 CROSSREFS Column 2 of A227089. Sequence in context: A086274 A174121 A128563 * A192978 A260546 A062421 Adjacent sequences:  A227082 A227083 A227084 * A227086 A227087 A227088 KEYWORD nonn AUTHOR R. H. Hardin, Jun 30 2013 STATUS approved

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Last modified January 26 17:17 EST 2020. Contains 331280 sequences. (Running on oeis4.)