sidef-scripts/Math/count_of_composite_numbers.sf

#!/usr/bin/ruby

# Daniel "Trizen" Șuteu
# Date: 06 June 2021
# https://github.com/trizen

# Count the number of composite numbers <= n.

# See also:
#   https://oeis.org/A065855

func composite_count(n) {
    n >= 4 || return 0
    n - prime_count(n) - 1
}

say 30.of(composite_count)