Project Euler 7

Euler07.fsx

let rec primes =
    let isPrime n =
        primes
        |> Seq.takeWhile (fun v -> v <= (float n |> sqrt |> int64))
        |> (not << Seq.exists (fun v -> n % v = 0L))
    let rec primes' n = seq {
        if isPrime n then
            yield n
        yield! primes' (n + 2L)
    }
    seq {
        yield 2L
        yield! primes' 3L
    } |> Seq.cache;;

primes |> Seq.nth 10000