OFFSET
1,2
COMMENTS
Here sigma(n,k) is the sum of the k-th powers of the divisors of n.
Logarithmic derivative of A198301.
FORMULA
L.g.f.: Sum_{n>=1} Sum_{k>=1} sigma(n,k) * x^(n*k)/n.
EXAMPLE
MATHEMATICA
a[n_] := DivisorSum[n, # * DivisorSigma[#, n/#] &]; Array[a, 40] (* Amiram Eldar, Aug 18 2023 *)
PROG
(PARI) {a(n)=sumdiv(n, d, d*sigma(n/d, d))}
(PARI) {a(n)=n*polcoeff(sum(m=1, n, sum(k=1, n\m, sigma(m, k)*x^(m*k)/m)+x*O(x^n)), n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 27 2012
STATUS
approved