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URL: https://oeis.org/A250017

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A250017
Number of length 3+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, 912, 13512, 106352, 558588, 2224848, 7259024, 20384352, 50937444, 115954256, 244606296, 484335696, 909078092, 1630002576, 2809238304, 4677097664, 7553346228, 11873110032, 18218051048, 27353482032, 40272132252, 58245315920
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = n^8 + (41/35)*n^7 + (56/15)*n^6 + (22/5)*n^5 + (19/3)*n^4 + (17/5)*n^3 - (16/15)*n^2 + (36/35)*n.
Conjectures from Colin Barker, Nov 10 2018: (Start)
G.f.: 4*x*(5 + 183*x + 1506*x^2 + 3974*x^3 + 3441*x^4 + 903*x^5 + 68*x^6) / (1 - x)^9.
a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>8.
(End)
EXAMPLE
Some solutions for n=4:
..0....2....0....0....1....3....3....2....0....2....1....2....2....0....1....2
..2....1....1....3....4....4....4....4....3....4....0....4....2....3....3....1
..1....4....3....4....0....1....0....1....2....2....1....0....2....3....2....0
..4....2....3....1....3....4....4....2....0....0....3....0....0....3....0....3
..1....4....1....0....0....0....0....0....0....0....3....4....0....1....0....4
..3....3....3....4....3....2....1....1....2....0....3....1....0....0....2....0
..0....2....2....1....0....0....4....3....0....4....1....3....1....2....0....4
..3....0....2....2....3....3....0....4....2....4....2....2....2....0....1....0
CROSSREFS
Row 3 of A250014.
Sequence in context: A192370 A113102 A285673 * A305116 A066802 A354814
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 10 2014
STATUS
approved