.NET (Core and Framework)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ParallelConsole
{
    class Program
    {
        static bool IsPrime(double x)
        {
            if (x < 2) return false;

            double sqrroot = Math.Ceiling(Math.Sqrt(x));
            bool isPrime = true;

            for (int i = 2; i <= sqrroot; i++)
            {
                if (x % i == 0)
                {
                    isPrime = false;
                    break;
                }
            }
            return isPrime;
        }

        static void helper(double i, DateTime dt)
        {
            if (i != 1)
                i = 3;

            while (i > 0 && i <= 100000)
            {
                if (IsPrime(i))
                    Console.WriteLine(i.ToString() + " : " + DateTime.Now.Subtract(dt).ToString());

                i += 4;
            }
        }

        static void Main(string[] args)
        {

            Console.WriteLine("Finding prime numbers(from 1.). Press Enter to start!");
            Console.ReadLine();

            DateTime startTimeSequential; TimeSpan sq = new TimeSpan();
            DateTime startTimeParallel; TimeSpan prl = new TimeSpan();

            //sequential
            startTimeSequential = DateTime.Now;
            for (int i = 1; i <= 2; i++)//loop two times
            {
                helper(i, startTimeSequential); // 1 for odd, 2 for alternate odd. check the numbers in two streams               
            }
            sq = DateTime.Now.Subtract(startTimeSequential);


            //parallel
            startTimeParallel = DateTime.Now;
            Parallel.For(1, 3, (i => { helper(i, startTimeParallel); }));

            prl = DateTime.Now.Subtract(startTimeParallel);
            Console.WriteLine("Total time sequential = " + sq.ToString());
            Console.WriteLine("Total time parallel (2) = " + prl.ToString());



            Console.ReadLine();
        }
    }
}