private double Kapital(int jahr)

    {
            double k0, z, k;

            k0 = 1000;
            z = 3.5/100;
            k = 1000;

            k = k0 * Math.Pow((1 + z), jahr);

            return k;

    }

        private void button1_Click(object sender, EventArgs e)
        {
            int i;



            for (i = 0; i < 6; i++)
            {
                textBox1.Text += i + " " + Kapital(i) + "\r\n";
            }