A068112 Denominator of coefficient of (-x^2)^n in F(x)*F(-x) where F(x)=sum(k>=0,x^k/(k!)^3).

1, 4, 768, 1555200, 20808990720, 9029615616000000, 1415988202438656000000, 536259842454308939366400000, 7188611938994779905746534400000000, 503281313253202450261043834781696000000

Offset

0,2

References

Bruce Berndt, Ramanujan's Notebooks Part II, Springer-Verlag; see Hypergeometric series, p. 62.

Links

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

Formula

F(x)*F(-x)=sum(n>=0, (3n)!/(n!)^3/((2n)!)^3*(-x^2)^n)

Mathematica

F[x_] := HypergeometricPFQ[{}, {1, 1}, x]; F[x]*F[-x] + O[x]^20 // CoefficientList[#, x^2]& // Denominator (* Jean-François Alcover, Nov 17 2016 *)

Crossrefs

Cf. A068113.

Sequence in context: A308141 A284813 A306254 * A007725 A102195 A114766

Adjacent sequences: A068109 A068110 A068111 * A068113 A068114 A068115

Keyword

easy,frac,nonn

Author

Benoit Cloitre, Mar 21 2002

Status

approved