OFFSET
1,1
FORMULA
a(n) = 4 * A034733(n).
G.f.: Sum_{k>=1} 2^(k+1)*x^k/(1 - 2*x^k). - Ilya Gutkovskiy, Sep 10 2019
a(n) ~ 2^(n+2). - Vaclav Kotesovec, Sep 11 2019
MATHEMATICA
Table[Sum[2^(d + n/d), {d, Divisors[n]}], {n, 1, 30}] (* Vaclav Kotesovec, Sep 11 2019 *)
PROG
(PARI) a(n) = if(n==0, 1, sumdiv(n, d, 2^d * 2^(n/d) )); \\ Joerg Arndt, Apr 14 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved