A225009 Number of n X 7 0..1 arrays with rows unimodal and columns nondecreasing.

29, 239, 1163, 4166, 12174, 30738, 69498, 144111, 278707, 508937, 885677, 1479452, 2385644, 3730548, 5678340, 8439021, 12277401, 17523187, 24582239, 33949058, 46220570, 62111270, 82469790, 108296955, 140765391, 181240749, 231304609

Offset

1,1

Links

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

Formula

Empirical: a(n) = (4/315)*n^7 + (1/5)*n^6 + (58/45)*n^5 + (35/8)*n^4 + (1507/180)*n^3 + (357/40)*n^2 + (2027/420)*n + 1.

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

G.f.: x*(29 + 7*x + 63*x^2 - 70*x^3 + 56*x^4 - 28*x^5 + 8*x^6 - x^7) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.

(End)

Example

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

Crossrefs

Column 7 of A225010.

Sequence in context: A126426 A126425 A224145 * A177419 A142559 A125366

Adjacent sequences: A225006 A225007 A225008 * A225010 A225011 A225012

Keyword

nonn

Author

R. H. Hardin, Apr 23 2013

Status

approved