Project Euler Problem 2: Even Fibonacci Numbers

The source code for this problem can be found here.

Problem Statement

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:

\(1, 2, 3, 5, 8, 13, 21, 34, 55, 89, \dots\)

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

Solution Discussion

Simply iterate over the Fibonacci numbers up to four million and sum all the even ones.

Solution Implementation

from itertools import takewhile

from lib.numbertheory import is_even
from lib.sequence import Fibonaccis


def solve():
    """ Compute the answer to Project Euler's problem #2 """
    upper_bound = 4000000
    numbers = [fib_i for fib_i in takewhile(lambda x: x <= upper_bound, Fibonaccis()) if is_even(fib_i)]
    answer = sum(numbers)
    return answer


expected_answer = 4613732

solutions.problem2.solve()

Compute the answer to Project Euler’s problem #2