A266936 Number of 3 X n binary arrays with rows lexicographically nondecreasing and columns lexicographically nondecreasing and row sums nondecreasing and column sums nonincreasing.

4, 7, 9, 12, 14, 19, 21, 26, 30, 35, 39, 46, 50, 57, 63, 70, 76, 85, 91, 100, 108, 117, 125, 136, 144, 155, 165, 176, 186, 199, 209, 222, 234, 247, 259, 274, 286, 301, 315, 330, 344, 361, 375, 392, 408, 425, 441, 460, 476, 495, 513, 532, 550, 571, 589, 610, 630, 651, 671

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..158

Formula

Empirical: a(n) = a(n-1) + a(n-2) - a(n-4) - a(n-5) + a(n-6).

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

Example

Some solutions for n=4:
..0..0..0..1....0..0..1..1....1..1..1..1....0..0..1..1....0..0..1..1
..1..1..1..0....1..1..0..1....1..1..1..1....1..1..0..0....1..1..0..0
..1..1..1..0....1..1..1..0....1..1..1..1....1..1..0..0....1..1..1..1

Crossrefs

Row 3 of A266935.

Sequence in context: A007073 A279054 A086824 * A080574 A189367 A310951

Adjacent sequences: A266933 A266934 A266935 * A266937 A266938 A266939

Keyword

nonn

Author

R. H. Hardin, Jan 06 2016

Status

approved