OFFSET
1,2
LINKS
FORMULA
a(n) = sigma_(A000040(n))(n).
a(n) = [x^n] Sum_{k>=1} k^prime(n)*x^k/(1 - x^k). - Ilya Gutkovskiy, Sep 26 2017
MAPLE
a:= n-> numtheory[sigma][ithprime(n)](n):
seq(a(n), n=1..15); # Alois P. Heinz, Feb 10 2020
MATHEMATICA
a[n_] := DivisorSigma[Prime[n], n]; Array[a, 13]
(* Second program: *)
a[n_] := SeriesCoefficient[Sum[k^Prime[n]*x^k/(1-x^k), {k, 1, n}], {x, 0, n}]; Array[a, 13] (* Jean-François Alcover, Sep 29 2017, from 2nd formula *)
PROG
(PARI) a(n) = sigma(n, prime(n)); \\ Michel Marcus, Jul 03 2015
(Magma) [DivisorSigma(NthPrime(n), n):n in [1..15]]; // Vincenzo Librandi, Jul 15 2015
(Python)
from sympy import divisor_sigma, prime
def A259673(n):
....return divisor_sigma(n, prime(n)) # Chai Wah Wu, Jul 20 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ilya Gutkovskiy, Jul 03 2015
EXTENSIONS
a(11) and a(12) from Anders Hellström, Jul 14 2015
STATUS
approved