PROJECT EULER #45

Link to Project Euler problem 45

Triangle, pentagonal, and hexagonal numbers are generated by the following formulae:

Triangle		Tn=n(n+1)/2		1, 3, 6, 10, 15, ...
Pentagonal		Pn=n(3n-1)/2		1, 5, 12, 22, 35, ...
Hexagonal		Hn=n(2n-1)		1, 6, 15, 28, 45, ...

It can be verified that T₂₈₅ = P₁₆₅ = H₁₄₃ = 40755.

Find the next triangle number that is also pentagonal and hexagonal.

using System;

namespace ProjectEuler
{
class Program
{
 static void Main()
 {
     //Problem 45
     DateTime start = DateTime.Now;
     for (double i = 1; i < 1000000; i++)
     {
         double triangle = i/2*(i + 1);
         for (double j = 1; j <= i; j++)
         {
             double pentagonal = j/2*(3*j - 1);
             if (triangle == pentagonal)
             {
                 for (double k = 1; k <= j; k++)
                 {
                     double hexagonal = k*(2*k - 1);
                     if ( triangle==hexagonal&&triangle>40755)
                     {
                         Console.WriteLine(triangle +" "+ pentagonal +" "+ hexagonal);
                         TimeSpan time = DateTime.Now - start;
                         Console.WriteLine("This took {0}", time);
                         Console.ReadKey();
                     }
                 }
             }
         }
     }
 }
}
}