2. Prove by instruction that the sum of the first n terms in the triangular sequence is the tetrahedral number given by [n(n+1)(n+2)]/6

3. Create the sequence of the sums in #2 for the powers of 10, viz., 1, 10, 100, 1000, 10000 and so on. Try using powers of 2 or powers of 3 instead?