Initial data commit

Task/Forward-difference/C-sharp/forward-difference.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+class Program
+{
+    static IEnumerable<int> ForwardDifference(IEnumerable<int> sequence, uint order = 1u)
+    {
+        switch (order)
+        {
+            case 0u:
+                return sequence;
+            case 1u:
+                return sequence.Skip(1).Zip(sequence, (next, current) => next - current);
+            default:
+                return ForwardDifference(ForwardDifference(sequence), order - 1u);
+        }
+    }
+
+    static void Main()
+    {
+        IEnumerable<int> sequence = new[] { 90, 47, 58, 29, 22, 32, 55, 5, 55, 73 };
+        do
+        {
+            Console.WriteLine(string.Join(", ", sequence));
+        } while ((sequence = ForwardDifference(sequence)).Any());
+    }
+}