include mpfr.e
atom t0 = time()
mpz z = mpz_init()
for i=1 to 17 do
    integer pi = get_prime(i)
    mpz_ui_pow_ui(z,2,pi)
    mpz_sub_ui(z,z,1)
    string zs = mpz_get_str(z),
           fs = mpz_factorstring(mpz_prime_factors(z,20000))
    if fs!=zs then zs &= " = "&fs end if
    printf(1,"2^%d-1 = %s\n",{pi,zs})
end for
string s = "600851475143"
mpz_set_str(z,s)
printf(1,"%s = %s\n",{s,mpz_factorstring(mpz_prime_factors(z,500))})
?elapsed(time()-t0)