OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..1000
FORMULA
G.f.: Sum_{n>0} x^n/(1-10*x^n).
a(n) ~ 10^(n-1). - Vaclav Kotesovec, Jun 05 2021
MATHEMATICA
A113999[n_]:= DivisorSum[n, 10^(#-1) &];
Table[A113999[n], {n, 40}] (* G. C. Greubel, Jun 26 2024 *)
PROG
(PARI) a(n)=if(n<1, 0, sumdiv(n, k, 10^(k-1)));
(Magma)
A113999:= func< n | (&+[10^(d-1): d in Divisors(n)]) >;
[A113999(n): n in [1..40]]; // G. C. Greubel, Jun 26 2024
(SageMath)
def A113999(n): return sum(10^(k-1) for k in (1..n) if (k).divides(n))
[A113999(n) for n in range(1, 41)] # G. C. Greubel, Jun 26 2024
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Nov 12 2005
STATUS
approved