ore_s_harmonic_numbers.sf

#!/usr/bin/ruby

# Ore's harmonic numbers

# Numbers n, such that H(n) is an integer:
#   [1, 6, 28, 140, 270, 496, 672, 1638, 2970, 6200, 8128, 8190, ...]

func H(n) {
    n * sigma0(n) / sigma(n)
}

each(1..10000, {|n|
    var h = H(n)
    if (h.is_int) {
        printf(" H(%4s) = %s\n", n, h)
    }
})