experimental-projects/oeis-research/Jinyuan Wang/Least totient number k > 1 such that n*k is a nontotient number, or 0 if no such number exists/prog.sf

#!/usr/bin/ruby

# Least totient number k > 1 such that n*k is a nontotient number, or 0 if no such number exists.
# https://oeis.org/A361058

# Try to find a(30) using powerful numbers.

var n = 30
var from = (2.5 * 10**10)
var to = int(1.2*from)

loop {

    say "Sieving range: #{[from, to]}"

    2.powerful(from, to).each {|k|
        if (k.is_totient && !(k*n -> is_totient)) {
            die "Found: a(#{n}) <= #{k}\n"
        }
    }

    from = to+1
    to = int(1.2*from)
}