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 A225894 Number of n X 2 binary arrays whose sum with another n X 2 binary array containing no more than a single 1 has rows and columns in lexicographically nondecreasing order. 1
 4, 12, 33, 78, 162, 304, 527, 858, 1328, 1972, 2829, 3942, 5358, 7128, 9307, 11954, 15132, 18908, 23353, 28542, 34554, 41472, 49383, 58378, 68552, 80004, 92837, 107158, 123078, 140712, 160179, 181602, 205108, 230828, 258897, 289454, 322642 (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) = (1/6)*n^4 + (1/6)*n^3 + (4/3)*n^2 + (1/3)*n + 2. Conjectures from Colin Barker, Sep 05 2018: (Start) G.f.: x*(4 - 8*x + 13*x^2 - 7*x^3 + 2*x^4) / (1 - x)^5. a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5. (End) EXAMPLE Some solutions for n=3: ..0..0....0..0....0..0....0..1....0..1....0..0....0..0....0..0....0..1....0..1 ..1..1....0..0....0..0....1..1....0..0....1..0....0..1....0..1....1..1....1..0 ..1..1....1..0....0..0....0..1....1..1....1..1....1..0....0..1....1..1....0..0 CROSSREFS Column 2 of A225900. Sequence in context: A265212 A295500 A168078 * A318637 A227554 A305778 Adjacent sequences: A225891 A225892 A225893 * A225895 A225896 A225897 KEYWORD nonn AUTHOR R. H. Hardin, May 20 2013 STATUS approved

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Last modified August 13 02:28 EDT 2024. Contains 375113 sequences. (Running on oeis4.)