t0 = time()
--for i=1 to 17 do
for i=18 to 25 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,20000000))
    if fs!=zs then zs &= " = "&fs end if
    printf(1,"2^%d-1 = %s\n",{pi,zs})
end for
s = "100000000000000000037"
mpz_set_str(z,s)
printf(1,"%s = %s\n",{s,mpz_factorstring(mpz_prime_factors(z,5000000))})
?elapsed(time()-t0)