login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A160619
a(n) = Sum_{d|n} phi(n/d)*2^(d+1), with a(0) = 0.
2
0, 4, 12, 24, 48, 80, 168, 280, 576, 1080, 2160, 4136, 8448, 16432, 33096, 65760, 131712, 262208, 525672, 1048648, 2099520, 4194960, 8392824, 16777304, 33564096, 67109200, 134234256, 268437672, 536904480, 1073741936, 2147554080, 4294967416, 8590066944
OFFSET
0,2
LINKS
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