601 Divisibility streaks.sf

#!/usr/bin/ruby

# Daniel "Trizen" Șuteu
# License: GPLv3
# Date: 30 April 2017
# https://github.com/trizen

# https://projecteuler.net/problem=601

# Runtime: 0.115s

func count(n, k) {
    var L      = lcm(1..n)
    var period = lcm(L, n + 1)/L
    var count  = floor((k - 2) / L)
    count - floor(count / period)
}

say sum(1..31, {|k| count(k, 4**k) })