Project Euler.net Answers

Problem 2

Solved on 2/29/2008

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 one million.

$pn = 1;
$pn2 = 0;
$answer = 0;
for($c = 1; $c < 1000000; $c=$pn+$pn2 ) {
  if(($c % 2) == 0 && $c < 1000000) $answer += $c;
  $pn2 = $pn;
  $pn = $c;
}
$answer = 1,089,154