A333610 Least number that reaches 1 after n iterations of the infinitary totient function A091732.

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

Links

Table of n, a(n) for n=0..30.

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

Cf. A003271, A007755, A091732, A333609.

Sequence in context: A188532 A181288 A255260 * A052418 A051800 A121432

Adjacent sequences: A333607 A333608 A333609 * A333611 A333612 A333613

Keyword

nonn,more

Author

Amiram Eldar, Mar 28 2020

Status

approved