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A266930 Number of n X 3 binary arrays with rows lexicographically nondecreasing and columns lexicographically nondecreasing and row sums nondecreasing and column sums nonincreasing. 1
2, 4, 9, 20, 44, 92, 182, 340, 605, 1028, 1680, 2651, 4058, 6045, 8793, 12518, 17484, 24001, 32438, 43222, 56853, 73901, 95024, 120965, 152570, 190786, 236681, 291440, 356388, 432986, 522854, 627768, 749685, 890738, 1053264, 1239799, 1453106 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 4*a(n-1) - 4*a(n-2) - 3*a(n-3) + 6*a(n-4) - 6*a(n-7) + 3*a(n-8) + 4*a(n-9) - 4*a(n-10) + a(n-11).

Empirical g.f.: x*(2 - 4*x + x^2 + 6*x^3 - x^5 - 4*x^6 + 4*x^7 + 3*x^8 - 4*x^9 + x^10) / ((1 - x)^7*(1 + x)^2*(1 + x + x^2)). - Colin Barker, Jan 10 2019.

EXAMPLE

Some solutions for n=4:

..0..0..1....0..0..0....0..0..0....0..0..0....0..1..1....0..0..0....0..0..1

..0..1..0....0..0..1....0..0..0....0..0..0....1..0..1....0..0..1....0..0..1

..1..0..0....1..1..0....0..0..0....1..1..1....1..1..0....0..1..0....1..1..0

..1..1..1....1..1..0....1..1..1....1..1..1....1..1..0....1..0..0....1..1..0

CROSSREFS

Column 3 of A266935.

Sequence in context: A175104 A123720 A179744 * A034007 A109975 A129891

Adjacent sequences:  A266927 A266928 A266929 * A266931 A266932 A266933

KEYWORD

nonn,changed

AUTHOR

R. H. Hardin, Jan 06 2016

STATUS

approved

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Last modified January 16 15:53 EST 2019. Contains 319195 sequences. (Running on oeis4.)