21.2.05
arithmetic fns to remember
- d(n)
- the number of positive divisors of n
- ρ(n)
- the sum of the positive divisors of n
- ω(n)
- the # of distinct primes dividing n
- Ω(n)
- the total # of prime factors of n
- φ(n)
- the # of a<n, a and n are co-prime
- μ(n)
- (-1)ω(n) if n is square-free, 0 otherwise
# posted by weierstrass @ 23:50 
