072 Counting fractions -- v2.sf

#!/usr/bin/ruby

# Daniel "Trizen" Șuteu
# Date: 25 July 2021
# https://github.com/trizen

# Sum of Euler phi function phi(k) for 2 <= k <= 10^6.

# https://projecteuler.net/problem=72

# Runtime: 0.205s

say dirichlet_sum(1e6, { .moebius }, { _ },
                       { .mertens }, { .faulhaber(1) })-1