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A289127
Numbers k such that uphi(k)/uphi(uphi(k)) > uphi(m)/uphi(uphi(m)) for all m < k, where uphi is the unitary totient function (A047994).
0
1, 3, 7, 31, 211, 2311, 32048, 512768, 9737984, 300690391, 6915878971, 8626257644
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
The unitary version of A289125.
Cf. A047994.
Sequence in context: A002585 A365021 A103785 * A289125 A083772 A093441
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Jun 25 2017
EXTENSIONS
a(10)-a(12) from Amiram Eldar, Mar 26 2023
STATUS
approved