Entries from 2007-03-15 to 1 day
Euler's phi function: number of coprimes of an integer m phi(m) = m*Prod(1-1/p) [where p: prime number and p|m] def phi(m) r = (2..m) primes = r.inject(r){|p, i| p.select{|n| n==i || n%i!=0}} primes.inject(m){|e, p| e%p==0 ? e/p*(p-1) : e}…