A249709 Number of length 3+3 0..n arrays with every four consecutive terms having the maximum of some two terms equal to the minimum of the remaining two terms.

20, 125, 440, 1153, 2524, 4893, 8688, 14433, 22756, 34397, 50216, 71201, 98476, 133309, 177120, 231489, 298164, 379069, 476312, 592193, 729212, 890077, 1077712, 1295265, 1546116, 1833885, 2162440, 2535905, 2958668, 3435389, 3971008, 4570753

Offset

1,1

Links

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

Formula

Empirical: a(n) = (1/15)*n^5 + 2*n^4 + 7*n^3 + 7*n^2 + (44/15)*n + 1.

Conjectures from Colin Barker, Nov 10 2018: (Start)

G.f.: x*(20 + 5*x - 10*x^2 - 12*x^3 + 6*x^4 - x^5) / (1 - x)^6.

a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.

(End)

Example

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

Crossrefs

Row 3 of A249707.

Sequence in context: A263545 A227057 A263543 * A250648 A250421 A073968

Adjacent sequences: A249706 A249707 A249708 * A249710 A249711 A249712

Keyword

nonn

Author

R. H. Hardin, Nov 04 2014

Status

approved