highly_composite_numbers.sf

#!/usr/bin/ruby

# Translation of:
#   https://gist.github.com/dario2994/fb4713f252ca86c1254d

# Generate all the highly composite numbers <= LIMIT.

const LIMIT = (ARGV ? ARGV[0].to_i : 10**8)

# Generates a list of the first primes (with product > LIMIT).
func gen_primes() {

    var primes = []
    var primes_product = 1

    for (var p = 2; primes_product <= LIMIT; p.next_prime!) {
        primes << p
        primes_product *= p
    }

    return primes
}

# Generates a list of the hcn <= LIMIT.
func gen_hcn() {

    var primes = gen_primes()
    var hcn = [[1, 1, []]]

    primes.each_kv {|i,p|

        var new_hcn = []

        hcn.each {|el|

            new_hcn << el

            next if (el[2].len < i)

            for e in (1 .. (p==2 ? LIMIT.ilog2 : el[2][i-1])) {

                var (n, sigma0, exps) = el...
                var new_exps = [exps...]

                n *= p**e
                sigma0 *= e+1
                new_exps << e

                break if (n > LIMIT)

                new_hcn << [n, sigma0, new_exps]
            }
        }

        hcn = [[1, 1, []]]

        new_hcn.sort.each {|el|
            if (el[1] > hcn[-1][1]) {
                hcn << el
            }
        }
    }

    return hcn.map{ .head }
}

say gen_hcn().join(', ')