Initial data commit

Task/Fibonacci-sequence/C-sharp/fibonacci-sequence-14.cs

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+using System;
+using BI = System.Numerics.BigInteger;
+
+class Program {
+
+  // returns the nth Fibonacci number without calculating 0..n-1
+  static BI oneFib(int n) {
+    BI z = (BI)1 << ++n;
+    return BI.ModPow(z, n, (z << n) - z - 1) % z;
+  }
+
+  // returns an array of Fibonacci numbers from the 0th to the nth
+  static BI[] fibTab(int n) {
+    var res = new BI[++n];
+    BI z = (BI)1 << 1, zz = z << 1;
+    for (int i = 0; i < n; ) {
+      res[i] = BI.ModPow(z, ++i, zz - z - 1) % z;
+      z <<= 1; zz <<= 2;
+    }
+    return res;
+  }
+
+  static void Main(string[] args) {
+    int n = 20;
+    Console.WriteLine("Fibonacci numbers 0..{0}: {1}", n, string.Join(" ",fibTab(n)));
+    n = 1000;
+    Console.WriteLine("Fibonacci({0}): {1}", n, oneFib(n));
+  }
+}