OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = 4*A034738(n). - Michel Marcus, May 07 2018
MATHEMATICA
a[n_]:= If[n<1, 0, Sum[EulerPhi[n/d] 2^(d+1), {d, Divisors[n]}]]; Table[a[n], {n, 0, 50}] (* G. C. Greubel, May 06 2018 *)
PROG
(PARI) a(n) = if (n==0, 0, sumdiv(n, d, eulerphi(n/d)*2^(d+1))); \\ Michel Marcus, May 07 2018; corrected Jun 14 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 21 2009
EXTENSIONS
Name edited by Michel Marcus, Jun 14 2022
STATUS
approved