
doi: 10.1137/0517085
The author studies the formal power series (everywhere divergent) \(F(z)=\sum^{\infty}_{r=1}a_ rz^ r\), where \(a_ r=r^ pw(r)(r!)^ m,\) \(p\geq 0\), \(m\geq 1\) are integers and w(r) is such that for some \(\sigma >0\), \(w(r)\sim \sum^{\infty}_{i=0}w_ ir^{-i- \sigma},\) as \(r\to \infty\). It is shown that the partial sums \(A_ r(z)\) of the above series can be represented as \(A_{r-1}(z)=A(z)a_ rz^ rg(r,z)\) where A(z) is the Borel-type sum of F(z) (defined by the author as a generalization of the Borel sum of F(z)) and for the converging factor g(r,z) an asymptotic expansion for \(r\to \infty\) and fixed z is obtained.
Convergence factors and summability factors, Abel, Borel and power series methods, Extrapolation to the limit, deferred corrections, asymptotic expansion, converging factor, Convergence and divergence of series and sequences, Borel summability, Singular perturbations for ordinary differential equations, formal power series, Asymptotic expansions of solutions to ordinary differential equations
Convergence factors and summability factors, Abel, Borel and power series methods, Extrapolation to the limit, deferred corrections, asymptotic expansion, converging factor, Convergence and divergence of series and sequences, Borel summability, Singular perturbations for ordinary differential equations, formal power series, Asymptotic expansions of solutions to ordinary differential equations
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