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A266423
Number of n X 3 binary arrays with rows and columns lexicographically nondecreasing and column sums nondecreasing.
1
4, 14, 39, 96, 212, 433, 826, 1493, 2575, 4270, 6841, 10639, 16114, 23845, 34555, 49147, 68725, 94637, 128501, 172257, 228199, 299035, 387927, 498560, 635189, 802719, 1006760, 1253717, 1550855, 1906400, 2329613, 2830904, 3421916, 4115651
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 5*a(n-1) - 8*a(n-2) + a(n-3) + 9*a(n-4) - 6*a(n-5) - 6*a(n-7) + 9*a(n-8) + a(n-9) - 8*a(n-10) + 5*a(n-11) - a(n-12).
Empirical g.f.: x*(4 - 6*x + x^2 + 9*x^3 - 6*x^4 - 6*x^6 + 9*x^7 + x^8 - 8*x^9 + 5*x^10 - x^11) / ((1 - x)^8*(1 + x)^2*(1 + x + x^2)). - Colin Barker, Jan 09 2019
EXAMPLE
Some solutions for n=4:
..0..0..1....0..0..1....0..0..0....0..0..0....0..0..1....0..0..0....0..0..1
..0..0..1....0..1..1....0..0..0....0..0..1....0..1..1....0..0..0....0..1..1
..1..1..0....1..1..0....0..0..1....0..1..1....0..1..1....0..0..0....1..1..1
..1..1..0....1..1..1....1..1..1....0..1..1....0..1..1....1..1..1....1..1..1
CROSSREFS
Column 3 of A266428.
Sequence in context: A141755 A064463 A130423 * A055484 A055279 A074083
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 29 2015
STATUS
approved