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

Author

R. H. Hardin, Dec 29 2015

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Column 3 of A266470.

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