The first and fifth terms of an A.P. are $$-14$$ and 2 respectively and the sum of its n terms is 40. The value of n is

Total number of elements in the power set of A containing 17 elements is

The sum of the series $$(1 + 2) + (1 + 2 + {2^2}) + (1 + 2 + {2^2} + {2^3}) + ....$$ upto $$n$$ terms is

If a, b, c are in A.P., $$b-a,c-b$$ and a are in G.P., then a : b : c is