A250389 Number of length 3+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, 146, 1208, 5848, 20518, 58114, 141344, 306816, 609846, 1129986, 1977272, 3299192, 5288374, 8190994, 12315904, 18044480, 25841190, 36264882, 49980792, 67773272, 90559238, 119402338, 155527840, 200338240, 255429590, 322608546

Offset

1,1

Comments

Row 3 of A250387.

Links

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

Formula

Empirical: a(n) = n^6 + (16/15)*n^5 + (13/6)*n^4 + (5/3)*n^3 - (1/6)*n^2 + (4/15)*n.

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

G.f.: 2*x*(3 + 52*x + 156*x^2 + 124*x^3 + 25*x^4) / (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:
..4....4....3....2....0....4....1....4....0....5....4....4....2....3....1....3
..3....0....0....2....1....0....1....0....4....3....5....2....4....0....2....1
..0....1....0....5....4....5....0....0....3....0....0....2....2....0....4....1
..5....5....2....5....5....3....0....2....6....1....2....4....6....1....0....5
..4....6....4....2....2....1....3....4....2....3....1....5....1....5....4....4
..2....3....1....1....6....4....6....1....6....2....3....2....6....2....3....5

Crossrefs

Sequence in context: A121473 A166837 A166809 * A358800 A063419 A065986

Adjacent sequences: A250386 A250387 A250388 * A250390 A250391 A250392

Keyword

nonn

Author

R. H. Hardin, Nov 20 2014

Status

approved