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A266465 Number of n X 3 binary arrays with rows and columns lexicographically nondecreasing and column sums nonincreasing. 1
2, 5, 12, 29, 67, 147, 303, 590, 1090, 1922, 3253, 5311, 8400, 12918, 19377, 28425, 40873, 57722, 80196, 109776, 148240, 197703, 260666, 340063, 439318, 562401, 713894, 899055, 1123895, 1395251, 1720873, 2109508, 2570998, 3116374, 3757967 (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) = 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*(2 - 5*x + 3*x^2 + 7*x^3 - 5*x^4 - x^5 - 3*x^6 + 7*x^7 - 7*x^9 + 5*x^10 - x^11) / ((1 - x)^8*(1 + x)^2*(1 + x + x^2)). - Colin Barker, Jan 10 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 3 of A266470.

Sequence in context: A274594 A062422 A320553 * A079864 A131045 A182555

Adjacent sequences:  A266462 A266463 A266464 * A266466 A266467 A266468

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 29 2015

STATUS

approved

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Last modified June 30 19:43 EDT 2022. Contains 354945 sequences. (Running on oeis4.)