A266542 Number of n X 3 binary arrays with rows and columns lexicographically nondecreasing and row and column sums nonincreasing.

2, 3, 5, 6, 8, 11, 13, 16, 20, 23, 27, 32, 36, 41, 47, 52, 58, 65, 71, 78, 86, 93, 101, 110, 118, 127, 137, 146, 156, 167, 177, 188, 200, 211, 223, 236, 248, 261, 275, 288, 302, 317, 331, 346, 362, 377, 393, 410, 426, 443, 461, 478, 496, 515, 533, 552, 572, 591, 611, 632

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 2*a(n-1) - a(n-2) + a(n-3) - 2*a(n-4) + a(n-5).

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

Example

Some solutions for n=6:
..0..1..1....0..1..1....0..0..1....0..1..1....0..1..1....0..1..1....0..0..1
..0..1..1....1..0..1....0..1..0....1..0..0....0..1..1....0..1..1....0..0..1
..1..0..1....1..1..0....0..1..0....1..0..0....0..1..1....1..0..0....0..1..0
..1..0..1....1..1..0....1..0..0....1..0..0....1..0..0....1..0..0....0..1..0
..1..1..0....1..1..0....1..0..0....1..0..0....1..0..0....1..0..0....1..0..0
..1..1..0....1..1..0....1..0..0....1..0..0....1..0..0....1..0..0....1..0..0

Crossrefs

Column 3 of A266547.

Sequence in context: A275341 A191884 A291693 * A095172 A179101 A127312

Adjacent sequences: A266539 A266540 A266541 * A266543 A266544 A266545

Keyword

nonn

Author

R. H. Hardin, Dec 31 2015

Status

approved