OFFSET
1,2
COMMENTS
Alaoglu and Erdős proved that lim sup sigma(phi(n))/n = oo, thus this sequence is infinite.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..55
Leon Alaoglu and Paul Erdős, A conjecture in elementary number theory, Bulletin of the American Mathematical Society, Vol. 50, No. 12 (1944), pp. 881-882.
Florian Luca and Carl Pomerance, On some problems of Makowski-Schinzel and Erdős concerning the arithmetical functions phi and sigma, Colloquium Mathematicae, Vol. 92, No. 1 (2002), pp. 111-130.
MATHEMATICA
a={}; rm=0; Do[r = DivisorSigma[1, EulerPhi[n]]/n; If[r>rm, rm=r; AppendTo[a, n]], {n, 1, 100000}]; a
PROG
(PARI) lista(nn) = {my(rmax = 0); for (n=1, nn, if ((r=sigma(eulerphi(n))/n) > rmax, rmax = r; print1(n, ", ")); ); } \\ Michel Marcus, Oct 18 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 15 2017
STATUS
approved