OFFSET
1,2
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..100
Igor E. Shparlinski, On the sum of iterations of the Euler function, Journal of Integer Sequences, Vol. 9 (2006), Article 06.1.6.
EXAMPLE
18 is in the sequence because phi(18)+phi(phi(18))+phi(phi(phi(18))) = 6 + 2 + 1 = 9, which divides 18.
MATHEMATICA
s[1]=1; s[n_] := Total@NestWhileList[EulerPhi, n, #>1 &] - n; Select[Range@ 1000, Mod[#, s@#] == 0 &] (* Giovanni Resta, May 25 2013 *)
PROG
(PARI) lista(nn) = {for (n=1, nn, s = 0; m = n; until (m == 1, m = eulerphi(m); s += m; ); if ((n % s == 0), print1(n, ", ")); ); } \\ Michel Marcus, May 25 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Jeffrey Shallit, Jan 22 2006
STATUS
approved