OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..2000
FORMULA
G.f.: Sum_{n>0} x^n/(1-3*x^n). - Vladeta Jovovic, Nov 14 2002
a(n) ~ 3^(n-2). - Vaclav Kotesovec, Sep 09 2014
a(n) = Sum_{d|n} 3^(d-1). - Seiichi Manyama, Jun 26 2019
MATHEMATICA
Rest[CoefficientList[Series[Sum[x^k/(1-3*x^k), {k, 1, 30}], {x, 0, 30}], x]] (* Vaclav Kotesovec, Sep 09 2014 *)
A034730[n_]:= DivisorSum[n, 3^(#-1) &];
Table[A034730[n], {n, 40}] (* G. C. Greubel, Jun 25 2024 *)
PROG
(PARI) {a(n) = sumdiv(n, d, 3^(d-1))} \\ Seiichi Manyama, Jun 26 2019
(Magma)
A034730:= func< n | (&+[3^(d-1): d in Divisors(n)]) >;
[A034730(n): n in [1..40]]; // G. C. Greubel, Jun 25 2024
(SageMath)
def A034730(n): return sum(3^(k-1) for k in (1..n) if (k).divides(n))
[A034730(n) for n in range(1, 41)] # G. C. Greubel, Jun 25 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved