What is the Recursive formula for the following sequence { 3, 5, 7, 9,... } *

Question

A.) a1=3;an=2an-1

B.) a1=3;an=an-1+2

C.) a1=2;an=an-1+3

D.) a1=2;an=3an-1+2

Answer 1

The sequence 3, 5, 7, 9, ...    has 3 as the first element (the base case in recursion).  So, a₁ = 3

That eliminates choices C and D.

 

Now, each term is 2 more than the previous term.

              a_n      =     2     +             a_n-1

 

That looks like answer B.