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A166338 a(n) = (4*n)!/n!. 6
1, 24, 20160, 79833600, 871782912000, 20274183401472000, 861733891296165888000, 60493719168990845337600000, 6526062423950732395020288000000, 1025113885554181044609786839040000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Integral representation as n-th moment of a positive function on a positive halfaxis (solution of the Stieltjes moment problem), in Maple notation: a(n)=int(x^n*((1/16*(2*Pi^(3/2)*sqrt(2)*hypergeom([], [1/2, 3/4], -(1/256)*x)*sqrt(x) -2*Pi*sqrt(2)*hypergeom([], [3/4, 5/4], -(1/256)*x)*GAMMA(3/4)*x^(3/4) +sqrt(Pi)*GAMMA(3/4)^2*hypergeom([], [5/4, 3/2], -(1/256)*x)*x))*sqrt(2)/(GAMMA(3/4)*x^(5/4)*Pi^(3/2))), x=0..infinity), n=0,1... .

This solution may not be unique.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..100

FORMULA

G.f.: sum(a(n)*x^n/(n!)^3,n=0..infinity)=hypergeom([1/4, 1/2, 3/4], [1, 1], 256*x).

a(n) ~ 2*(1-1/(16*n)+1/(512*n^2)+331/(122880*n^3)+O(1/n^4)))*(2^n)^8/(((1/n)^n)^3*(exp(n))^3),n->infinity.

1/a(n) = n!*[x^n](cosh(x^(1/4))+cos(x^(1/4)))/2. - Peter Luschny, Jul 12 2012

MAPLE

A166338_list := proc(n) u:=z^(1/4); (cosh(u)+cos(u))/2:series(%, z, n+2):

seq(1/(i!*coeff(%, z, i)), i=0..n) end: A166338_list(9); # Peter Luschny, Jul 12 2012

MATHEMATICA

Table[(4n)!/n!, {n, 0, 10}] (* Harvey P. Dale, May 30 2015 *)

PROG

(MAGMA) [Factorial(4*n) / Factorial(n): n in [0..15]]; // Vincenzo Librandi, May 10 2016

CROSSREFS

Sequence in context: A067746 A111404 A167066 * A258874 A188961 A153303

Adjacent sequences:  A166335 A166336 A166337 * A166339 A166340 A166341

KEYWORD

nonn

AUTHOR

Karol A. Penson, Oct 12 2009

STATUS

approved

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Last modified December 1 10:42 EST 2021. Contains 349427 sequences. (Running on oeis4.)