OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
G.f.: Sum_{k>=1} k*x^k/(1 - x^k) - 6*k*x^(6*k)/(1 - x^(6*k)). - Ilya Gutkovskiy, Mar 25 2017
Sum_{k=1..n} a(k) ~ (5*Pi^2/72) * n^2. - Amiram Eldar, Oct 04 2022
Dirichlet g.f. (1-6^(1-s))*zeta(s-1)*zeta(s), but not multiplicative. - R. J. Mathar, May 17 2023
MATHEMATICA
Table[Sum[Boole[Mod[d, 6]>0] d , {d, Divisors[n]}], {n, 100}] (* Indranil Ghosh, Mar 25 2017 *)
Table[Total[Select[Divisors[n], Mod[#, 6]!=0&]], {n, 100}] (* Harvey P. Dale, Feb 25 2020 *)
PROG
(PARI) for(n=1, 100, print1(sumdiv(n, d, ((d%6)>0)*d), ", ")) \\ Indranil Ghosh, Mar 25 2017
(Python)
from sympy import divisors
print([sum([i for i in divisors(n) if i%6]) for n in range(1, 101)]) # Indranil Ghosh, Mar 25 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 25 2017
STATUS
approved