OFFSET
1,3
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1500
EXAMPLE
A007497(9) = 168 = 2^3*3*7, so a(n) = 3.
MATHEMATICA
f[1] = 2; f[n_] := f[n] = DivisorSigma[1, f[n - 1]]; Table[IntegerExponent[f[n], 2], {n, 70}] (* Amiram Eldar, Mar 27 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Allan C. Wechsler, May 01 2015
EXTENSIONS
More terms from Michel Marcus, May 01 2015
STATUS
approved