Q2

Problem 2

19 October 2001

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

A:
fib 1 = 1
fib 2 = 2
fib n = fib(n-1) + fib(n-2)

sum [x|x<-[fib n | n<-[1..4000000]], even x]