A160619 a(n) = Sum_{d|n} phi(n/d)*2^(d+1), with a(0) = 0.
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
Keywords
Links
- G. C. Greubel, Table of n, a(n) for n = 0..1000
Programs
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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 *) -
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
Formula
a(n) = 4*A034738(n). - Michel Marcus, May 07 2018
Extensions
Name edited by Michel Marcus, Jun 14 2022