A249710 Number of length 4+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.

28, 221, 896, 2601, 6172, 12789, 24032, 41937, 69052, 108493, 164000, 239993, 341628, 474853, 646464, 864161, 1136604, 1473469, 1885504, 2384585, 2983772, 3697365, 4540960, 5531505, 6687356, 8028333, 9575776, 11352601, 13383356

Offset

1,1

Links

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

Formula

Empirical: a(n) = (7/15)*n^5 + 5*n^4 + 11*n^3 + 8*n^2 + (38/15)*n + 1.

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

G.f.: x*(28 + 53*x - 10*x^2 - 20*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:
..1....3....4....5....2....1....2....6....6....5....1....2....2....3....2....2
..3....5....3....0....6....0....3....1....3....3....3....2....4....3....4....3
..6....1....1....2....3....1....0....1....2....5....3....1....2....5....5....3
..3....3....3....2....3....1....2....1....3....5....4....2....2....3....4....3
..3....3....4....2....3....1....2....4....3....5....3....2....1....3....1....4
..0....3....3....1....3....2....2....1....5....3....3....5....2....3....4....3
..6....2....2....6....1....0....2....1....1....5....1....1....4....5....6....2

Crossrefs

Row 4 of A249707.

Sequence in context: A053135 A340908 A297614 * A269621 A269437 A236355

Adjacent sequences: A249707 A249708 A249709 * A249711 A249712 A249713

Keyword

nonn

Author

R. H. Hardin, Nov 04 2014

Status

approved