Permutations and Combinations

Question

# Find the sum to n terms of the sequence given by

The given sequence is   defined by

Let   denote the sum of n terms

∴
=

Since the series in the first bracket is a G.P. series with 1st term 2, common ratio 2 and the series in the second bracket is an A.P. with 1st term 3, common difference 3.

∴