If you only want 3 variables to be used to make the fibonacci sequence happen, then the could should be:
int num1 = 0;
int num2 = 0;
int num3 = 1;
Console.Write("How many numbers of the fibbonacci sequence do you want printed out?: ");
int amountOfNumPrint = Convert.ToInt32(Console.ReadLine());
for(int i = 0; i < amountOfNumPrint; i++)
{
if (num3 < 0)
{
Console.WriteLine("We cannot go past the number above.");
i = amountOfNumPrint + 15;
continue;
}
Console.WriteLine(num3);
num1 = num2;
num2 = num3;
num3 = num1 + num2;
}
But if it is 3 variables in general, then I am not experienced enough to do that, and will let the rest of the community battle out.