OFFSET
1,3
COMMENTS
a(n) = 1 for n >= 2, n from A049642.
EXAMPLE
MATHEMATICA
f[n_] := Divide @@ DivisorSigma[{1, 0}, n]; a[n_] := Length @ NestWhileList[f, n, IntegerQ[#] && # > 1 &] - 1; Array[a, 100] (* Amiram Eldar, Mar 19 2021 *)
PROG
(PARI) a(n) = if (n==1, 0, my(nb=1, k); while(denominator(k=sigma(n)/numdiv(n)) == 1, n = k; nb++); nb); \\ Michel Marcus, Mar 21 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Mar 19 2021
STATUS
approved