A254700 Number of length 2+4 0..n arrays with every five consecutive terms having the maximum of some two terms equal to the minimum of the remaining three terms.

34, 267, 1116, 3341, 8142, 17255, 33048, 58617, 97882, 155683, 237876, 351429, 504518, 706623, 968624, 1302897, 1723410, 2245819, 2887564, 3667965, 4608318, 5731991, 7064520, 8633705, 10469706, 12605139, 15075172, 17917621, 21173046

Offset

1,1

Links

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

Formula

Empirical: a(n) = (4/5)*n^5 + (19/3)*n^4 + (34/3)*n^3 + (29/3)*n^2 + (73/15)*n + 1.

Conjectures from Colin Barker, Dec 17 2018: (Start)

G.f.: x*(34 + 63*x + 24*x^2 - 30*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=10:
..2....9....1....3....8....3....2....4....2....0....0....8....9....2....1....3
..9....0....0....7....1....3....4....3....5....2....6....1....1....2....1....4
..7....9....2....1....3....4....4....4....9....6....9....2....1....5....1....7
..3....0....0....2....3....6....5....2....5....2....6....0...10....1....7....4
..3....0....0....2...10....3....4....3....5....2....8....1....1....2....0....4
..1....9....7....9....8....0....3....8....1....3....0....2....0....7....1....2

Crossrefs

Row 2 of A254698.

Sequence in context: A209944 A371403 A081219 * A241698 A159776 A295917

Adjacent sequences: A254697 A254698 A254699 * A254701 A254702 A254703

Keyword

nonn

Author

R. H. Hardin, Feb 05 2015

Status

approved