[discrete math]Consider he sequence {si} defined recursively for positive integers i 1 as follows:

s1 = 1

si = 2si-1+1

c. write a recursive algorithm that takes a positive integer n for input and outputs Sn

input: positive n

output: Sn

1. input some positive integer n

2. if n =1 return n

3. ?

4. return Sn

can someone help me with this code? I was just stuck on step 3 but i have no clue if the other steps are right. I just need them in normal english no code required