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A179442 a(n) = ((n-1)! * (n+1)!) / n. 1
2, 3, 16, 180, 3456, 100800, 4147200, 228614400, 16257024000, 1448500838400, 158018273280000, 20713561989120000, 3212195459235840000, 581636820654489600000, 121600871304831959040000 (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^2) = (Product_(k=1,2,...,n) k * (k+1)) / (n^2).

a(n) = A175430(n) / n = A001044(n-1) * (n+1) = ((n -1)^2)! * (n+1).

G.f.: 1 + G(0), where G(k)= 1 + x*(k+1)/(1 - (k+2)/(k+2 + 1/G(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Jul 08 2013

EXAMPLE

a(5) = ((5-1)! * (5+1)!) / 5 = (4! * 6!) / 5 = (24 * 720) / 5 = 17280 / 5 = 3456.

a(5) = ((5 -1)!^2) * (5+1) = 24^2 * 6 = 3456.

CROSSREFS

Sequence in context: A006247 A052318 A141309 * A215638 A057997 A290590

Adjacent sequences:  A179439 A179440 A179441 * A179443 A179444 A179445

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jul 14 2010

STATUS

approved

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Last modified October 18 10:28 EDT 2017. Contains 293507 sequences.