A193388 Sum of even divisors of phi(n).

0, 0, 2, 2, 6, 2, 8, 6, 8, 6, 12, 6, 24, 8, 14, 14, 30, 8, 26, 14, 24, 12, 24, 14, 36, 24, 26, 24, 48, 14, 48, 30, 36, 30, 56, 24, 78, 26, 56, 30, 84, 24, 64, 36, 56, 24, 48, 30, 64, 36, 62, 56, 84, 26, 84, 56, 78, 48, 60, 30, 144, 48, 78, 62, 120, 36, 96

Offset: 1

Author

Michel Lagneau, Jul 25 2011

Keywords

• nonn

Examples

			a(13) = 24 because phi(13) = 12 and the sum of the 4 even divisors { 2, 4, 6, 12} is 24.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384

Crossrefs

Cf. A000010, A062402, A146076, A193454.

Cf. also A193322, A193386.

Programs

Mathematica

Table[Total[Select[Divisors[EulerPhi[n]], EvenQ[ # ]&]], {n, 58}]

PARI

A193388(n) = { my(s=eulerphi(n)); sumdiv(s,d,(!(d%2))*d); }; \\ Antti Karttunen, Dec 05 2017

Formula

a(n) = A146076(A000010(n)) = A062402(n) - A193454(n). - Antti Karttunen, Dec 05 2017