A267233 Number of length-4 0..n arrays with no following elements greater than or equal to the first repeated value.

6, 47, 176, 470, 1030, 1981, 3472, 5676, 8790, 13035, 18656, 25922, 35126, 46585, 60640, 77656, 98022, 122151, 150480, 183470, 221606, 265397, 315376, 372100, 436150, 508131, 588672, 678426, 778070, 888305, 1009856, 1143472, 1289926

Offset

1,1

Comments

Row 4 of A267232.

Links

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

Formula

Empirical: a(n) = n^4 + (17/6)*n^3 + 2*n^2 + (1/6)*n.

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

G.f.: x*(6 + 17*x + x^2) / (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=6:
..4....5....2....2....0....4....4....5....0....4....3....2....0....4....0....3
..3....3....4....0....5....2....0....6....3....5....4....4....3....3....2....6
..1....3....2....5....5....3....1....2....5....5....2....1....0....2....4....4
..4....0....6....4....4....1....4....1....4....3....3....3....6....4....2....6

Crossrefs

Cf. A267232.

Sequence in context: A256160 A184725 A232495 * A027012 A160609 A267203

Adjacent sequences: A267230 A267231 A267232 * A267234 A267235 A267236

Keyword

nonn

Author

R. H. Hardin, Jan 12 2016

Status

approved