Euler_2

#-------------------------------------------------------------------------------
# Name:        Euler_2
# Purpose:
#
# Author:      Stewart
#
# Created:     24/07/2012
# Copyright:   (c) Stewart 2012
# Licence:     <your licence>
#-------------------------------------------------------------------------------
#!/usr/bin/env python

# 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.



def fib_even(limit, x, n):
    res = 0
    while x < limit:
        if x%2 == 0:
            res = res + x
        if n%2 == 0:
            res = res + n
        x = x + n
        n = n + x

    return res

print fib_even(4000000, 1,  2)