OFFSET
1,2
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..16384
Eric Weisstein's World of Mathematics, Distinct Prime Factors
FORMULA
a(n) = a(omega(n)) + 1 for n > 1, where omega() is the number of distinct prime factors.
EXAMPLE
If n = 6 the trajectory is {6, 2, 1}. Its length is 3, thus a(6) = 3.
MATHEMATICA
f[n_] := Length[NestWhileList[ PrimeNu, n, # != 1 &]]; Array[f, 105]
a[1] = 1; a[n_] := a[n] = a[PrimeNu[n]] + 1; Table[a[n], {n, 105}]
PROG
(Python)
from sympy import primefactors
def a(n): return 1 if n==1 else a(len(primefactors(n))) + 1 # Indranil Ghosh, Jun 03 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jun 01 2017
STATUS
approved