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 A061163 a(n) = (10n)!*n!/((5n)!*(4n)!*(2n)!). 8
 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 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 February 28 11:08 EST 2020. Contains 332323 sequences. (Running on oeis4.)