open System  // from stackoverflow.com/q/49219103/849891
   // by stackoverflow.com/users/1462221/patrick-stevens   
 
let sieveOutPrime p numbers =
   numbers
   |> Seq.filter (fun n -> n % p <> 0)
 
let primesLessThan n =
    let removeFirstPrime = function
       | s when Seq.isEmpty s -> None
       | s -> Some(Seq.head s, sieveOutPrime (Seq.head s) (Seq.tail s))
 
    let remainingPrimes =
       seq {3..2..n}
       |> Seq.unfold removeFirstPrime
 
    seq { yield 2; yield! remainingPrimes }
 
primesLessThan 1000000 |> Seq.skip 700 
                    |> Seq.take 10 
                    |> Seq.iter( fun n -> printf "%d " n )

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