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A250016 Number of length 2+5 0..n arrays with no six consecutive terms having the maximum of any three terms equal to the minimum of the remaining three terms. 1
20, 520, 5200, 30360, 125780, 412160, 1140160, 2776080, 6119220, 12455960, 23755600, 42913000, 74043060, 122832080, 196951040, 306535840, 464739540, 688361640, 998559440, 1421646520, 1989983380, 2742965280, 3728112320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = n^7 + 2*n^6 + 4*n^5 + 5*n^4 + (17/3)*n^3 + 3*n^2 - (2/3)*n.

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

G.f.: 20*x*(1 + 4*x + x^2)*(1 + 14*x + 23*x^2 + 4*x^3) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.

(End)

EXAMPLE

Some solutions for n=5:

..2....2....1....2....5....0....2....2....1....1....1....5....0....3....1....1

..3....4....2....0....1....1....0....4....1....1....5....0....5....2....2....3

..0....4....5....2....2....3....4....5....1....3....3....5....1....2....5....2

..0....5....3....5....4....4....0....0....3....2....0....2....2....5....3....0

..0....1....4....5....1....5....4....5....4....0....4....1....5....4....4....4

..1....1....2....3....4....5....5....0....5....4....1....5....3....1....1....5

..3....3....0....2....3....1....1....0....4....0....5....0....0....4....2....1

CROSSREFS

Row 2 of A250014.

Sequence in context: A008270 A130186 A130033 * A337352 A180882 A202920

Adjacent sequences:  A250013 A250014 A250015 * A250017 A250018 A250019

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 10 2014

STATUS

approved

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Last modified May 26 13:59 EDT 2022. Contains 354092 sequences. (Running on oeis4.)