Finding Fibonacci sequence in C#. [Project Euler Exercise]

Question

I\'m having some trouble with this problem in Project Euler.

Here\'s what the question asks:

Each new term in the Fibonacci sequence is generated by adding t

Answer 1

Here's a nice way to find Fibonnaci numbers.

IEnumerable Fibs()
{
    for(BigInteger a = 0,b = 1;;b = a + (a = b))
        yield return b;
}