This course teaches mathematical induction, the method for proving a statement for every natural number at once. You start with the principle of finite induction and the stronger principle of complete induction, and learn the standard way to set out a proof. You then collect the standard sums of natural numbers, squares, cubes, fourth powers, odd and even numbers, recall A.P., G.P. and A.G.P. formulas, and learn to find general terms. The final lesson applies induction to divisibility, shows how to find the divisor with a G.C.D., lists standard results and introduces congruence notation.