OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..386
N. J. A. Sloane, Transforms
FORMULA
a(n) = [x^n] Sum_{k>=1} sigma_n(k)*x^k/(1 - x^k).
a(n) = Sum_{d|n} d^n*tau(n/d).
a(n) ~ n^n. - Vaclav Kotesovec, Feb 16 2020
MAPLE
with(numtheory): seq(coeff(series(add(sigma[n](k)*x^k/(1-x^k), k=1..n), x, n+1), x, n), n = 1 .. 20); # Muniru A Asiru, Oct 28 2018
MATHEMATICA
Table[Sum[DivisorSigma[n, d], {d, Divisors[n]}] , {n, 19}]
Table[SeriesCoefficient[Sum[DivisorSigma[n, k] x^k/(1 - x^k), {k, 1, n}], {x, 0, n}], {n, 19}]
PROG
(PARI) a(n) = sumdiv(n, d, sigma(d, n)); \\ Michel Marcus, Oct 28 2018
(Python)
from sympy import divisor_sigma, divisors
def A321141(n):
return sum(divisor_sigma(d, 0)*(n//d)**n for d in divisors(n, generator=True)) # Chai Wah Wu, Feb 15 2020
(Magma) [&+[DivisorSigma(n, d):d in Divisors(n)]:n in [1..20]]; // Vincenzo Librandi, Feb 16 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 28 2018
STATUS
approved