Problem 2 - Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed four million

// June 9th, 2009 // Project Euler

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, …

Find the sum of all the even-valued terms in the sequence which do not exceed four million.

2 Responses to “Problem 2 - Find the sum of all the even-valued terms in the Fibonacci sequence which do not exceed four million”

  1. Scott Weaver says:
    June 9, 2009 at 10:52 am

    3524576? :D

    <?php

    $l = 4000000; // limit
    $y = $z = $sum = 1;

    for($i=0;$sum<=$l;$i++)
    {
    $x = $y+$z;
    $z = $y; $y = $x; $lsum = $sum;
    $sum += $x;
    }

    printf(”%d”, $lsum);

  2. Johannes Heuel says:
    December 12, 2009 at 4:14 am

    max = 4 * 10**6

    def fibo(a, b):
    if (a > max):
    return 0
    if (a%2 == 0):
    return a + fibo(b, a+b)
    else:
    return fibo(b, a+b)

    print fibo(1, 2)

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