A249961 Number of length 1+5 0..n arrays with no six consecutive terms having the maximum of any two terms equal to the minimum of the remaining four terms.

15, 285, 2010, 8790, 28785, 77595, 181860, 383580, 745155, 1355145, 2334750, 3845010, 6094725, 9349095, 13939080, 20271480, 28839735, 40235445, 55160610, 74440590, 99037785, 130066035, 168805740, 216719700, 275469675, 346933665

Offset

1,1

Comments

Row 1 of A249960.

Links

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

Formula

Empirical: a(n) = n^6 + 3*n^5 + 5*n^4 + 5*n^3 + (3/2)*n^2 - (1/2)*n.

Conjectures from Colin Barker, Aug 21 2017: (Start)

G.f.: 15*x*(1 + x)^2*(1 + 10*x + x^2) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.

(End)

Example

Some solutions for n=6:
..1....0....3....4....2....2....3....4....3....1....0....4....4....1....0....0
..3....4....1....2....4....5....1....2....3....3....1....2....1....6....0....3
..3....5....3....5....3....5....3....0....6....5....0....4....6....4....3....4
..5....3....1....3....0....6....2....3....6....2....2....1....5....1....6....1
..0....2....3....5....4....5....3....1....0....5....4....1....1....3....1....6
..4....0....2....1....4....3....3....6....1....0....3....2....2....5....3....4

Crossrefs

Sequence in context: A095654 A279167 A249960 * A177074 A069405 A125055

Adjacent sequences: A249958 A249959 A249960 * A249962 A249963 A249964

Keyword

nonn

Author

R. H. Hardin, Nov 09 2014

Status

approved