prime_sieve_seq_gen.fs

let sieve upperbound =
    let ar = Array.create (upperbound+1) 1
    
    for i in 2.. (ar.Length - 1) do
        let endi = int (floor (float (upperbound/i)))
        for j in i..endi  do
            ar.[i * j] <- 0
    seq{for i in 2..(ar.Length - 1) do if ar.[i] = 1 then yield i}