A266465 Number of n X 3 binary arrays with rows and columns lexicographically nondecreasing and column sums nonincreasing.

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

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