6 kyu
link to kata
my solution
Give the summation of all even numbers in a Fibonacci sequence up to, but not including, the number passed to your function. Or, in other words, sum all the even Fibonacci numbers that are lower than the given number n (n is not the nth element of Fibonacci sequence) without including n.
The Fibonacci sequence is a series of numbers where the next value is the addition of the previous two values. The series starts with 0 and 1:
0 1 1 2 3 5 8 13 21...
For example:
fibonacci(0)==0
fibonacci(33)==10
fibonacci(25997544)==19544084