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A175430 a(n) = (n-1)! * (n+1)! 2
2, 6, 48, 720, 17280, 604800, 29030400, 1828915200, 146313216000, 14485008384000, 1738201006080000, 248562743869440000, 41758540970065920000, 8142915489162854400000, 1824013069572479385600000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..15.

FORMULA

a(n) = (Product_(k=1,2,...,n) k*A020725(k)) / n;

a(n) = (Product_(k=1,2,...,n) k*(k+1)) / n.

a(n) = (-1) * A129464(n) = A179442(n) * n. [Jaroslav Krizek, Jul 22 2010]

a(n) = 2*A010791(n). - Michel Marcus, Feb 03 2016

EXAMPLE

a(5) = (5-1)! * (5+1)! = 4! * 6! = 24 * 720 = 17280.

a(5) = ((1*2) * (2*3) * (3*4) * (4*5) * (5*6)) / 5 = 17280.

PROG

(PARI) a(n) = (n-1)! * (n+1)!; \\ Michel Marcus, Feb 03 2016

CROSSREFS

Sequence in context: A052587 A052735 A052717 * A129464 A003053 A113296

Adjacent sequences:  A175427 A175428 A175429 * A175431 A175432 A175433

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, May 10 2010

STATUS

approved

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Last modified December 7 17:28 EST 2016. Contains 278890 sequences.