130 Composites with prime repunit property.sf

#!/usr/bin/ruby

# Daniel "Trizen" Șuteu
# Date: 21 September 2019
# Edit: 30 March 2023
# https://github.com/trizen

# https://projecteuler.net/problem=130

# Runtime: 0.516s

2..Inf -> lazy.grep {|n| n.is_composite }\
              .grep {|n| n.is_coprime(10) }\
              .grep {|n| (Mod(10, n)**(n-1) - 1)/9 == 0 }\
              .first(25).sum.say