module _55

open System.Numerics

let lynchrels =

    let isLynchrel n =
        let revInt (n:bigint) =
            n
            |> (string)
            |> common.revString
            |> (fun s -> BigInteger.TryParse(s) |> snd)

        let rec isLynchrelRec (n:bigint,d) =
            match (n + (revInt n)), d with
            | _,0 -> true
            | n,_ when ((string) >> common.isPalindrome) n -> false
            | n,d -> isLynchrelRec (n, d-1)
        isLynchrelRec (n,50)

    [|1I..10000I|]
    |> Array.filter isLynchrel
    |> Array.length