Project Euler #002

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.

let rec fib n1 n2 iterations =
    if iterations = 1 then
        n2
    else
        fib n2 (n1 + n2) (iterations-1)

let rec fiblist iterations =
    let n = fib 1 1 iterations
    if n > 4000000 then
        []
    else
        n :: fiblist (iterations + 1)

let even x = (x % 2 = 0)
List.fold (fun acc x -> if (even x) then acc + x else acc + 0) 0 (fiblist 1)