- #!/usr/bin/ruby
- # Daniel "Trizen" Șuteu
- # Date: 09 February 2017
- # https://github.com/trizen
- # Squarefree Numbers
- # https://projecteuler.net/problem=193
- # Formula for counting the number of squarefree numbers <= n:
- # S(n) = Sum_{k=1..floor(sqrt(n))} moebius(k) * floor(n/k^2)
- # Runtime: 0.291s (previously: ~6 seconds).
- say squarefree_count(2**50) # built-in
|
