A250390 Number of length 4+3 0..n arrays with no four consecutive terms having the maximum of any two terms equal to the minimum of the remaining two terms.

6, 274, 3384, 21950, 96866, 331128, 944272, 2352468, 5279310, 10902342, 21040360, 38386530, 66792362, 111607580, 180080928, 281826952, 429363798, 638727066, 930164760, 1328918374, 1866095154, 2579636576, 3515388080, 4728275100

Offset

1,1

Comments

Row 4 of A250387.

Links

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

Formula

Empirical: a(n) = n^7 + (19/30)*n^6 + (51/20)*n^5 + (17/12)*n^4 - (1/4)*n^3 + (19/20)*n^2 - (3/10)*n.

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

G.f.: 2*x*(3 + 113*x + 680*x^2 + 1107*x^3 + 547*x^4 + 70*x^5) / (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=5;
..5....4....3....3....0....1....3....2....0....4....1....1....1....2....4....2
..5....5....2....2....2....0....0....0....2....1....1....2....0....4....3....3
..2....5....4....4....4....2....4....3....0....2....5....0....5....5....2....4
..0....2....0....1....4....4....5....5....1....4....3....5....0....0....5....0
..1....3....4....4....1....4....5....0....2....1....4....1....3....1....4....4
..3....4....3....3....3....3....2....0....5....1....1....3....0....2....2....1
..0....5....2....4....5....1....1....5....3....2....2....0....3....5....1....0

Crossrefs

Sequence in context: A348701 A233234 A281694 * A284071 A254628 A211080

Adjacent sequences: A250387 A250388 A250389 * A250391 A250392 A250393

Keyword

nonn

Author

R. H. Hardin, Nov 20 2014

Status

approved