A161217 a(n) = Sum_{d|n} phi(n/d)^2*2^(d+1).

0, 4, 12, 32, 56, 128, 192, 400, 640, 1232, 2304, 4496, 8608, 16960, 33456, 66304, 132096, 263168, 526320, 1049872, 2100352, 4196480, 8393904, 16779152, 33565952, 67111488, 134235840, 268441424, 536906720, 1073744960, 2147560704, 4294970896, 8590069760

Offset: 0

Author

N. J. A. Sloane, Nov 21 2009

Keywords

• nonn

Crossrefs

Cf. A000010, A053635, A160620.

Programs

Maple

a:= proc(n) uses numtheory;
      add(phi(n/d)^2*2^(d+1), d=divisors(n))
    end:
seq(a(n), n=0..32);  # Alois P. Heinz, Jun 24 2021

PARI

a(n) = if (n, sumdiv(n, d, eulerphi(n/d)^2*2^(d+1)), 0); \\ Michel Marcus, Jun 24 2021

Formula

a(n) = 2*A160620(n). - Jon Maiga / Georg Fischer, Jun 22 2021