Concavity properties for certain linear combinations of Stirling numbers

Abstract

In the notation of Riordan ([5], p. 33), the Stirling numbers, s(n, k) and S(n, k), of the first and second kind respectively are defined by the relation where (x)n = x(x − 1) … (x − n + 1) is the factorial power function. They have been used by Jordan ([3], p. 184) to define the numbers C(m, k) and D(m, k), as linear combinations of s(n, k) and S(n, k) respectively, given by where and and where and D(m, O.