%N Smallest k such that A002217(k)=n.
%C Least number which becomes prime or 0 or 4 after n-1 iterations of f(x) = sum of prime factors of x (cf. A001414). Agrees with A048133 except for the second term.
%C a(21) <= 536226160966. a(22) <= 2681130804805. a(23) <= 8512643845707. - Donovan Johnson
%Y Cf. A002217, A001414, A048133.
%A _Klaus Brockhaus_, Jul 27 2006
%E Edited comment and a(19)-a(20) from _Donovan Johnson_, Oct 16 2010