OFFSET
1,2
LINKS
Paul Erdős and M. V. Subbarao, On the iterates of some arithmetic functions, The theory of arithmetic functions (Proc. Conf., Western Michigan Univ., Kalamazoo, Mich. 1971), Lecture Notes in Math., 251, pp. 119-125, Springer, Berlin, 1972. [alternate link]
MATHEMATICA
uphi[n_] := If[n==1, 1, (Times @@ (Table[ #[[1]]^ #[[2]] - 1, {1} ] & /@ FactorInteger[n]))[[1]]]; a = {}; k=1; rmax = 0; While[Length[a]<8, s = uphi[ k]; s2 = uphi[ s]; r = s/s2; If[r > rmax, AppendTo[a, k]; rmax = r]; k++]; a
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Jun 25 2017
EXTENSIONS
a(10)-a(12) from Amiram Eldar, Mar 26 2023
STATUS
approved