number of prime powers
- Who knows a good approximate formula for the number of prime powers up
to x (without simple prime numbers):
N = sum(1)(p^n <= x), p prime, n>1 ?
Suggestion: N ~ sqrt(x ln x) / ((ln ln x)^(ln ln x))
Hardy's formula (1999) N ~ sqrt(x)*ln(x) is only an upper bound and not
what I am looking for.
Werner D. Sand