PROJECT EULER #27

Link to Project Euler problem 27

Euler published the remarkable quadratic formula:

n² + n + 41

It turns out that the formula will produce 40 primes for the consecutive values n = 0 to 39. However, when n = 40, 40² + 40 + 41 = 40(40 + 1) + 41 is divisible by 41, and certainly when n = 41, 41² + 41 + 41 is clearly divisible by 41.

Using computers, the incredible formula n² - 79n + 1601 was discovered, which produces 80 primes for the consecutive values n = 0 to 79. The product of the coefficients, -79 and 1601, is -126479.

Considering quadratics of the form:

n² + an + b, where a < 1000 and b < 1000

where n is the modulus/absolute value of n
e.g. 11 = 11 and -4 = 4

Find the product of the coefficients, a and b, for the quadratic expression that produces the maximum number of primes for consecutive values of n, starting with n = 0.

using System;

namespace project_euler
{
   class Program
   {
       static void Main()
       {
           //Problem 27
           DateTime start = DateTime.Now;
           int result = 0, max = 0;
           for (int i = -999; i < 1000; i++)
           {
               for (int j = -999; j < 1000; j++)
               {
                   int n = 0, number = 0;
                   while (true)
                   {
                       number = n*n + i*n + j;
                       if (!IsPrime(number))
                           break;
                       n++;
                   }
                   if (n>max)
                   {
                       max = n;
                       result = i*j;
                   }
               }
           }
           Console.WriteLine(result);
           TimeSpan time = DateTime.Now - start;
           Console.WriteLine("This took {0}", time);
           Console.ReadKey();
       }
       public static bool IsPrime(int n)
       {
           if (n < 2)
               return false;
           if (n == 2)
               return true;
           for (long i = 2; i <= Math.Sqrt(n); i++)
           if (n%i == 0)
               return false;
           return true;
       }
   }
}