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A230346
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Number of permutations of [2n+6] in which the longest increasing run has length n+6.
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3
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1, 14, 231, 4512, 103194, 2721600, 81591840, 2746068480, 102661518960, 4224849995520, 189917647920000, 9263565222912000, 487461283781472000, 27533206366009344000, 1661865400404937728000, 106768864984887705600000, 7275718977990226283520000
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OFFSET
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0,2
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COMMENTS
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Also the number of ascending runs of length n+6 in the permutations of [2n+6].
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LINKS
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FORMULA
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a(n) = (n+5)*(n^2+9*n+11)*(2*n+6)!/(n+8)! for n>0, a(0) = 1.
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MAPLE
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a:= proc(n) option remember; `if`(n<2, 1+13*n, 2*(2*n+5)*(n+5)*
(n+3)*(n^2+9*n+11)*a(n-1)/((n+4)*(n+8)*(n^2+7*n+3)))
end:
seq(a(n), n=0..25);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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