Gregory coefficients Gn, also known as reciprocal logarithmic numbers, Bernoulli numbers of the second kind, or Cauchy numbers of the first kind, are the rational numbers
Contents
- Computation and representations
- Bounds and asymptotic behavior
- Series with Gregory coefficients
- Generalizations
- References
that occur in the Maclaurin series expansion of the reciprocal logarithm
Gregory coefficients are alternating Gn = (−1)n−1|Gn| and decreasing in absolute value. These numbers are named after James Gregory who introduced them in 1670 in the numerical integration context. They were subsequently rediscovered by many famous mathematicians and often appear in works of modern authors who do not recognize them.
Computation and representations
The simplest way to compute Gregory coefficients is to use the recurrence formula
with G1 = 1/2. Gregory coefficients may be also computed explicitly via the following differential
the integral
Schröder's integral formula
or the finite summation formula
where s(n,ℓ) are the signed Stirling numbers of the first kind.
Bounds and asymptotic behavior
The Gregory coefficients satisfy the bounds
given by Johan Steffensen. These bounds were later improved by various authors. The best known bounds for them were given by Blagouchine. In particular,
Asymptotically, at large index n, these numbers behave as
More accurate description of Gn at large n may be found in works of Van Veen, Davis, Coffey, Nemes and Blagouchine.
Series with Gregory coefficients
Series involving Gregory coefficients may be often calculated in a closed-form. Basic series with these numbers include
where γ = 0.5772156649... is Euler's constant. These results are very old, and their history may be traced back to the works of Gregorio Fontana and Lorenzo Mascheroni. More complicated series with the Gregory coefficients were calculated by various authors. Kowalenko, Alabdulmohsin and some other authors calculated
Alabdulmohsin also gives these identities
Candelperger, Coppo and Young showed that
where Hn are the harmonic numbers. Blagouchine provides the following identities
where li(z) is the integral logarithm and
Generalizations
Various generalizations are possible for the Gregory coefficients. Many of them may be obtained by modifying the parent generating equation. For example, Van Veen consider
and hence
Equivalent generalizations were later proposed by Kowalenko and Rubinstein. In a similar manner, Gregory coefficients are related to the generalized Bernoulli numbers
see, so that
Jordan defines polynomials ψn(s) such that
and call them Bernoulli polynomials of the second kind. From the above, it is clear that Gn = ψn(0). Carlitz generalized Jordan's polynomials ψn(s) by introducing polynomials β
and therefore
Blagouchine introduced numbers Gn(k) such that
and studied their asymptotics at large n. Clearly, Gn = Gn(1). A different generalization of the same kind was also proposed by Komatsu
so that Gn = cn(1)/n! Numbers cn(k) are called by the author poly-Cauchy numbers. Coffey defines polynomials
and therefore |Gn| = Pn+1(1).