This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A333609 #12 Apr 07 2020 17:10:41 %S A333609 0,1,2,3,4,2,3,3,4,4,5,3,4,3,4,5,6,4,5,4,4,5,6,3,4,4,6,5,6,4,5,5,5,6, %T A333609 4,4,5,5,4,4,5,4,5,5,6,6,7,5,6,4,6,5,6,6,5,5,5,6,7,4,5,5,6,7,6,5,6,6, %U A333609 6,4,5,4,5,5,6,7,5,4,5,5,6,5,6,5,8,5,6 %N A333609 The number of iterations of the infinitary totient function iphi (A091732) required to reach from n to 1. %H A333609 Amiram Eldar, <a href="/A333609/b333609.txt">Table of n, a(n) for n = 1..10000</a> %e A333609 a(6) = 2 since there are 2 iterations from 6 to 1: iphi(6) = 2 and iphi(2) = 1. %t A333609 f[p_, e_] := p^(2^(-1 + Position[Reverse @ IntegerDigits[e, 2], 1])); iphi[1] = 1; iphi[n_] := Times @@ (Flatten@(f @@@ FactorInteger[n]) - 1); a[n_] := Length @ NestWhileList[iphi, n, # != 1 &] - 1; Array[a, 100] %Y A333609 Cf. A003434, A049865, A091732. %K A333609 nonn %O A333609 1,3 %A A333609 _Amiram Eldar_, Mar 28 2020