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A333610
Least number that reaches 1 after n iterations of the infinitary totient function A091732.
1
1, 2, 3, 4, 5, 11, 17, 47, 85, 227, 257, 919, 1229, 2459, 4369, 9839, 30865, 101503, 148157, 438499, 828297, 2201671, 3316617, 11055391, 35354993, 140810491, 188991053, 377982107, 848170377, 1704741139, 6933926513
OFFSET
0,2
FORMULA
A333609(a(n)) = n.
MATHEMATICA
f[p_, e_] := p^(2^(-1 + Position[Reverse @ IntegerDigits[e, 2], 1])); iphi[1] = 1; iphi[n_] := Times @@ (Flatten@(f @@@ FactorInteger[n]) - 1); numiter[n_] := Length @ NestWhileList[iphi, n, # != 1 &] - 1; n = 0; seq = {}; Do[If[numiter[k] == n, AppendTo[seq, k]; n++], {k, 1, 1000}]; seq
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Mar 28 2020
STATUS
approved