func is_long_prime(p) {

    for d in (divisors(p-1)) {
        if (powmod(10, d, p) == 1) {
            return (d+1 == p)
        }
    }

    return false
}

say "Long primes ≤ 500:"
say primes(500).grep(is_long_prime).join(' ')

for n in ([500, 1000, 2000, 4000, 8000, 16000, 32000, 64000]) {
    say ("Number of long primes ≤ #{n}: ", primes(n).count_by(is_long_prime))
}