func is_duffinian(n) {
    n.is_composite && n.is_coprime(n.sigma)
}

say "First 50 Duffinian numbers:"
say 50.by(is_duffinian)

say "\nFirst 15 Duffinian triplets:"
15.by{|n| ^3 -> all {|k| is_duffinian(n+k) } }.each {|n|
    printf("(%s, %s, %s)\n", n, n+1, n+2)
}