1. Considering the previous two exercises, . . .
(a) . . . draw the first four square numbers.
(b) . . . draw the first four triangular numbers.
(c) . . . find a recurrence and a closed form for the square numbers.
(d) . . . find a recurrence and a closed form for the triangular numbers.
2. Challenge: Consider the k-figurate numbers. The first k-figurate number can be represented by a dot; the second k-figurate number can be represented by k dots that represent vertices of a k-gon. Find a recurrence and a closed form for the k-figurate numbers.