Add A019434 Fermat Primes sequence (TheAlgorithms#299)

Author: OleksiiHe

Algorithms.Tests/Sequences/FermatPrimesSequenceTests.cs

@@ -0,0 +1,19 @@
+using System.Linq;
+using System.Numerics;
+using Algorithms.Sequences;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace Algorithms.Tests.Sequences
+{
+    public class FermatPrimesSequenceTests
+    {
+        [Test]
+        public void All5ElementsCorrect()
+        {
+            var sequence = new FermatPrimesSequence().Sequence.Take(5);
+            sequence.SequenceEqual(new BigInteger[] { 3, 5, 17, 257, 65537 })
+                .Should().BeTrue();
+        }
+    }
+}

Algorithms/Sequences/FermatPrimesSequence.cs

@@ -0,0 +1,36 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Numerics;
+
+namespace Algorithms.Sequences
+{
+    /// <summary>
+    ///     <para>
+    ///         Sequence of Fermat primes: primes of the form 2^(2^k) + 1, for some k >= 0.
+    ///     </para>
+    ///     <para>
+    ///         Wikipedia: https://wikipedia.org/wiki/Fermat_number.
+    ///     </para>
+    ///     <para>
+    ///         OEIS: https://oeis.org/A019434.
+    ///     </para>
+    /// </summary>
+    public class FermatPrimesSequence : ISequence
+    {
+        /// <summary>
+        /// Gets sequence of Fermat primes.
+        /// </summary>
+        public IEnumerable<BigInteger> Sequence
+        {
+            get
+            {
+                var fermatNumbers = new FermatNumbersSequence().Sequence.Take(5);
+
+                foreach (var n in fermatNumbers)
+                {
+                    yield return n;
+                }
+            }
+        }
+    }
+}

README.md

@@ -118,6 +118,7 @@ This repository contains algorithms and data structures implemented in C# for ed
     * [A007318 Binomial](./Algorithms/Sequences/BinomialSequence.cs)
     * [A010051 Binary Prime Constant](./Algorithms/Sequences/BinaryPrimeConstantSequence.cs)
     * [A011557 Powers of 10](./Algorithms/Sequences/PowersOf10Sequence.cs)
+    * [A019434 Fermat Primes](./Algorithms/Sequences/FermatPrimesSequence.cs)
     * [A181391 Van Eck's](./Algorithms/Sequences/VanEcksSequence.cs)
   * [String](./Algorithms/Strings)
     * [Longest Consecutive Character](./Algorithms/Strings/GeneralStringAlgorithms.cs)