Initial data commit

Task/Van-Eck-sequence/F-Sharp/van-eck-sequence-1.fs

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+// Generate Van Eck's Sequence. Nigel Galloway: June 19th., 2019
+let ecK()=let n=System.Collections.Generic.Dictionary<int,int>()
+          Seq.unfold(fun (g,e)->Some(g,((if n.ContainsKey g then let i=n.[g] in n.[g]<-e;e-i else n.[g]<-e;0),e+1)))(0,0)

Task/Van-Eck-sequence/F-Sharp/van-eck-sequence-2.fs

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+ecK() |> Seq.take 50 |> Seq.iter(printf "%d "); printfn "";;

Task/Van-Eck-sequence/F-Sharp/van-eck-sequence-3.fs

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+ecK() |> Seq.skip 990 |> Seq.take 50|> Seq.iter(printf "%d "); printfn "";;

Task/Van-Eck-sequence/F-Sharp/van-eck-sequence-4.fs

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+open System.Collections.Generic
+let VanEck() =
+    let rec _vanEck (num:int) (pos:int) (lastOccurence:Dictionary<int, int>) =
+        match lastOccurence.TryGetValue num with
+        | (true, position) ->
+            set num pos (pos - position) lastOccurence
+        | _ ->
+            set num pos 0 lastOccurence
+    and set num pos next lastOccurenceByNumber = seq {
+            lastOccurenceByNumber.[num] <- pos
+            yield next
+            yield! _vanEck next (pos + 1) lastOccurenceByNumber
+        }
+
+    seq {
+        yield 0
+        yield! _vanEck 0 1 (new Dictionary<int, int>())
+    }
+
+VanEck() |> Seq.take 10 |> Seq.map (sprintf "%i") |> String.concat " " |> printfn "The first ten terms of the sequence : %s"
+VanEck() |> Seq.skip 990 |> Seq.take 10 |> Seq.map (sprintf "%i") |> String.concat " " |> printfn "Terms 991 - to - 1000 of the sequence : %s"