Catalan.cs

        Console.Write("Enter number between 1 and 100 (n):");
        int n = int.Parse(Console.ReadLine());
        if (1 < n && n < 100)
        {
            BigInteger doubleN = 1;
            BigInteger nPlus = 1;
            BigInteger num = 1;

            for (int i = 2; i <= n * 2; i++)
            {
                doubleN *= i;

                if (i <= n + 1)
                {
                    nPlus *= i;

                }

                if (i <= n)
                {
                    num *= i;

                }
            }

            BigInteger result = doubleN / (nPlus * num);
            Console.WriteLine("Catalan(n) = " + result);

        }