A229795 Number of 2 X 2 0..n arrays with rows and columns in lexicographically nondecreasing order.

7, 29, 86, 205, 421, 777, 1324, 2121, 3235, 4741, 6722, 9269, 12481, 16465, 21336, 27217, 34239, 42541, 52270, 63581, 76637, 91609, 108676, 128025, 149851, 174357, 201754, 232261, 266105, 303521, 344752, 390049, 439671, 493885, 552966, 617197

Offset

1,1

Links

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

Formula

Empirical: a(n) = (1/3)*n^4 + (7/6)*n^3 + (13/6)*n^2 + (7/3)*n + 1.

Conjectures from Colin Barker, Sep 21 2018: (Start)

G.f.: x*(7 - 6*x + 11*x^2 - 5*x^3 + 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=2:
..0..2....1..2....1..1....1..2....0..1....0..0....0..2....1..2....0..0....0..2
..1..0....2..2....1..1....2..1....1..0....2..2....0..2....2..0....0..1....2..2

Crossrefs

Row 2 of A229794.

Sequence in context: A375656 A079796 A242727 * A114043 A331767 A166189

Adjacent sequences: A229792 A229793 A229794 * A229796 A229797 A229798

Keyword

nonn

Author

R. H. Hardin, Sep 29 2013

Status

approved