Consider the following sequence. 0, 1, 3, 6, 10, 15, 21,...
(a) List the next two terms of the sequence.
(b) Assuming the sequence is denoted by A 1, A 2, A 3 ,..., give an explicit formula for AN.
(c) Assuming the sequence is denoted by P0, P1, P2,..., give an explicit formula for PN.
