A007480 a(n) = denominator of sum_{k=1..n} k^(-4).

1, 16, 1296, 20736, 12960000, 12960000, 31116960000, 497871360000, 40327580160000, 40327580160000, 590436101122560000, 590436101122560000, 16863445484161436160000, 16863445484161436160000, 16863445484161436160000, 269815127746582978560000

Offset: 1

Author

N. J. A. Sloane, Mira Bernstein

Keywords

• nonn
• easy
• frac

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• T. D. Noe, Table of n, a(n) for n=1..200
• D. Y. Savio, E. A. Lamagna and S.-M. Liu, Summation of harmonic numbers, pp. 12-20 of E. Kaltofen and S. M. Watt, editors, Computers and Mathematics, Springer-Verlag, NY, 1989.

Crossrefs

Cf. A007410.

Programs

Mathematica

Denominator[Accumulate[1/Range[20]^4]] (* Harvey P. Dale, Dec 25 2013 *)

Formula

a(n) = denominator of (Pi^4/90 - zeta(4, n+1)). - Arkadiusz Wesolowski, Nov 23 2012

Denominators of coefficients in expansion of PolyLog(4, x)/(1 - x). - Ilya Gutkovskiy, Apr 10 2017