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A230382 Number of ascending runs of length n in the permutations of [2n]. 2
1, 2, 21, 312, 5880, 133920, 3575880, 109549440, 3788104320, 145957593600, 6201593798400, 288084016281600, 14525808782284800, 790129980896256000, 46120599397192320000, 2875600728738017280000, 190740227037467627520000, 13411608375592258191360000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..300

FORMULA

For n>0, a(n) = (n^2+n+1)*(2*n)!/((n+2)*n!). - Vaclav Kotesovec, Oct 18 2013

MAPLE

a:= proc(n) option remember; `if`(n<2, 1+n,

      2*(2*n-1)*(n+1)*(n^2+n+1)*a(n-1)/((n+2)*(n^2-n+1)))

    end:

seq(a(n), n=0..25);

CROSSREFS

A diagonal of A122843.

Sequence in context: A097627 A094797 A234525 * A196629 A196637 A240997

Adjacent sequences:  A230379 A230380 A230381 * A230383 A230384 A230385

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Oct 17 2013

STATUS

approved

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Last modified August 17 17:25 EDT 2017. Contains 290648 sequences.