Question

A sequence is recursively defined as a(n)=2a(n-2) for values of n>2. Find the seventh term of the sequence if a(1)=0 and a(2)=1

Answer 1

a(7) = 21

Explanation:

Using the recursive formula and a(1) = 0, a(2) = 1 , then

a(3) = a(2) + 2a(1) = 1 + 2(0) = 1 + 0 = 1

a(4) = a(3) + 2a(2) = 1 + 2(1) = 1 + 2 = 3

a(5) = a(4) + 2a(3) = 3 + 2(1) = 3 + 2 = 5

a(6) = a(5) + 2a(4) = 5 + 2(3) = 5 + 6 = 11

a(7) = a(6) + 2a(5) = 11 + 2(5) = 11 + 10 = 21