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A132341 Main diagonal of A132339. 1
1, 2, 10, 168, 4290, 136136, 4938024, 196125600, 8318177010, 370784099400, 17184867259560, 821870841735840, 40334204896057800, 2022686389717666848, 103312949950998743200, 5360873347802169267840, 282015983963437605168210 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

G. Kreweras, Sur une classe de problèmes de dénombrement liés au treillis des partitions des entiers, Cahiers du Bureau Universitaire de Recherche Opérationnelle}, Institut de Statistique, Université de Paris, 6 (1965), see equation (67) circa p. 82.

FORMULA

a(n) is found by setting h=k=n in A(n,k) = 2(-1)^(h+k) (h+k-1)! (2h+2k-3)! / ( h! k! (2h-1)! (2k-1)! ), h >= 1, k >= 1.

a(n) ~ 2^(6*n - 9/2) / (Pi*n^3). - Vaclav Kotesovec, Mar 27 2016

PROG

(PARI) a(n) = if (n, 2*(4*n-3)!/(n!^2*(2*n-1)!), 1); \\ Michel Marcus, Mar 27 2016

CROSSREFS

Sequence in context: A328812 A126451 A260122 * A069994 A063573 A086675

Adjacent sequences:  A132338 A132339 A132340 * A132342 A132343 A132344

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Nov 08 2007

EXTENSIONS

More terms from Max Alekseyev, Sep 12 2009

STATUS

approved

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Last modified April 15 13:12 EDT 2021. Contains 342977 sequences. (Running on oeis4.)