A249708 Number of length 2+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.

14, 69, 208, 485, 966, 1729, 2864, 4473, 6670, 9581, 13344, 18109, 24038, 31305, 40096, 50609, 63054, 77653, 94640, 114261, 136774, 162449, 191568, 224425, 261326, 302589, 348544, 399533, 455910, 518041, 586304, 661089, 742798, 831845, 928656

Offset

1,1

Links

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

Formula

Empirical: a(n) = (1/2)*n^4 + 4*n^3 + (11/2)*n^2 + 3*n + 1.

Conjectures from Colin Barker, Nov 09 2018: (Start)

G.f.: x*(2 - x)*(7 + 3*x + 3*x^2 - x^3) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.

(End)

Example

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

Crossrefs

Row 2 of A249707.

Sequence in context: A238822 A244943 A347673 * A008354 A051879 A236157

Adjacent sequences: A249705 A249706 A249707 * A249709 A249710 A249711

Keyword

nonn

Author

R. H. Hardin, Nov 04 2014

Status

approved