Euler OOM

//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

/**


Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.


**/


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {

        public static void Main(string[] args)
        {
           new Program();

        }

        public Program(){
            double x = 1;
            double sum = 0;
            double findNXHold = findNX(x);
            while(findNXHold <= 55){
                if(findNXHold % 2 == 0){
                    sum+= findNXHold;
                }
                x = x+3;
                findNXHold = findNX(x);

            }
            Console.WriteLine(sum);
        }

        public double findNX(double x){
            if(x == 0){
              return 1;
            }
            if(x == 1){
             return 2;
            }
            return 2*findNX(x-2) + findNX(x-3);
        }



    }
}