using Mpir.NET;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading.Tasks;

namespace MersenneHint
{
    class Program
    {
        static void Main(string[] args)
        {
            var logFactor = Math.Log10(2);
            int i = 0;
            var primes = GetPrimes(74000000, 75000000);
            var sw = Stopwatch.StartNew();
            Parallel.ForEach(primes, p =>
            {
                lock(lockObj) i++;
                if (i % 100 == 0)
                    Console.WriteLine(sw.Elapsed + ": " + i);
                var digits = (int)Math.Floor(p * logFactor) + 1;
                using (var tenPowerEnd = mpz_t.Ten.Power(digits - 19391387 + 1))
                using (var twoPowerMod = mpz_t.Two.PowerMod(p, tenPowerEnd))
                using (var powMinOne = twoPowerMod - 1)
                using (var tenPowerStart = mpz_t.Ten.Power(digits - 19391387 + 1 - 7))
                using (var div = powMinOne.Divide(tenPowerStart))
                {
                    var mpSecStr = div.ToString();
                    if (mpSecStr == "2718281")
                        Console.WriteLine(p);
                }
            });
            Console.WriteLine("done");
            Console.ReadLine();
        }
        static readonly object lockObj = new object();
        static IList<int> GetPrimes(int from, int to)
        {
            var primes = new List<int>();
            for (mpz_t i = new mpz_t(from).NextPrimeGMP(); i <= to; i = i.NextPrimeGMP())
            {
                if (i.ToString().Contains("42") && !alreadyFactored.Contains((int)i))
                    primes.Add((int)i);
            }
            return primes;
        }

        static readonly HashSet<int> alreadyFactored = new HashSet<int> { ..... }; // pastebin doesn't like this crazy long list, fill it in yourself from http://www.mersenne.org/report_factors/
    }
}