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A061163 a(n) = (10n)!*n!/((5n)!*(4n)!*(2n)!). 7
1, 630, 1385670, 3528923580, 9540949030470, 26651569523959380, 75998432812419471900, 219813190240007470094520, 642409325786050322446410310, 1892390644737640220059489996260 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

According to page 781 of the cited reference the generating function F(x) for a(n) is algebraic but not obviously so and the minimal polynomial satisfied by F(x) is quite large.

This sequence is the particular case a = 5, b = 1 of the following result (see Bober, Theorem 1.2): let a, b be nonnegative integers with a > b and GCD(a,b) = 1. Then (2*a*n)!*(b*n)!/((a*n)!*(2*b*n)!*((a-b)*n)!) is an integer for all integer n >= 0. Other cases include A061162 (a = 3, b = 1), A211419 (a = 3, b = 2) and A211420(a = 4, b = 1) and A211421 (a = 4, b = 3). The o.g.f. sum {n >= 1} a(n)*z^n is algebraic over the field of rational functions Q(z) (see Rodriguez-Villegas). - Peter Bala, Apr 10 2012

REFERENCES

M. Kontsevich and D. Zagier, Periods, in Mathematics Unlimited - 2001 and Beyond, Springer, Berlin, 2001, pp. 771-808.

LINKS

Table of n, a(n) for n=0..9.

J. W. Bober, Factorial ratios, hypergeometric series, and a family of step functions, 2007, arXiv:0709.1977v1 [math.NT], Jour. of the London Math. Soc., Vol. 79, Issue 2, 422-444.

F. Rodriguez-Villegas, Integral ratios of factorials and algebraic hypergeometric functions. arXiv:math.NT/0701362

FORMULA

n*(4*n-3)*(2*n-1)*(4*n-1)*a(n) -10*(10*n-9)*(10*n-7)*(10*n-3)*(10*n-1)*a(n-1)=0. - R. J. Mathar, Oct 26 2014

MAPLE

A061123 := n->(10*n)!*n!/((5*n)!*(4*n)!*(2*n)!);

CROSSREFS

Cf. A061163, A061164. A211419, A211420, A211421.

Sequence in context: A185849 A058832 A225390 * A045168 A270802 A119504

Adjacent sequences:  A061160 A061161 A061162 * A061164 A061165 A061166

KEYWORD

easy,nonn

AUTHOR

Richard Stanley, Apr 17 2001

STATUS

approved

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Last modified December 11 01:07 EST 2019. Contains 329910 sequences. (Running on oeis4.)