A225894 Number of n X 2 binary arrays whose sum with another n X 2 binary array containing no more than a single 1 has rows and columns in lexicographically nondecreasing order.

4, 12, 33, 78, 162, 304, 527, 858, 1328, 1972, 2829, 3942, 5358, 7128, 9307, 11954, 15132, 18908, 23353, 28542, 34554, 41472, 49383, 58378, 68552, 80004, 92837, 107158, 123078, 140712, 160179, 181602, 205108, 230828, 258897, 289454, 322642

Offset

1,1

Links

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

Formula

Empirical: a(n) = (1/6)*n^4 + (1/6)*n^3 + (4/3)*n^2 + (1/3)*n + 2.

Conjectures from Colin Barker, Sep 05 2018: (Start)

G.f.: x*(4 - 8*x + 13*x^2 - 7*x^3 + 2*x^4) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.

(End)

Example

Some solutions for n=3:
..0..0....0..0....0..0....0..1....0..1....0..0....0..0....0..0....0..1....0..1
..1..1....0..0....0..0....1..1....0..0....1..0....0..1....0..1....1..1....1..0
..1..1....1..0....0..0....0..1....1..1....1..1....1..0....0..1....1..1....0..0

Crossrefs

Column 2 of A225900.

Sequence in context: A265212 A295500 A168078 * A318637 A227554 A305778

Adjacent sequences: A225891 A225892 A225893 * A225895 A225896 A225897

Keyword

nonn

Author

R. H. Hardin, May 20 2013

Status

approved