Summation of divergent power series by means of factorial series

  • Authors:
  • Ernst Joachim Weniger

  • Affiliations:
  • Institut für Physikalische und Theoretische Chemie, Universität Regensburg, D-93040 Regensburg, Germany

  • Venue:
  • Applied Numerical Mathematics
  • Year:
  • 2010

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Abstract

Factorial series played a major role in Stirling's classic book Methodus Differentialis (1730), but now only a few specialists still use them. This article wants to show that this neglect is unjustified, and that factorial series are useful numerical tools for the summation of divergent (inverse) power series. This is documented by summing the divergent asymptotic expansion for the exponential integral E"1(z) and the factorially divergent Rayleigh-Schrodinger perturbation expansion for the quartic anharmonic oscillator. Stirling numbers play a key role since they occur as coefficients in expansions of an inverse power in terms of inverse Pochhammer symbols and vice versa. It is shown that the relationships involving Stirling numbers are special cases of more general orthogonal and triangular transformations.