In Tara's math class, each student made up a number pattern for classmates to identify. These are the numbers that Tara wrote. Find the pattern and identify the first and seventh numbers in the table.

a. first number:
b. seventh number:

Tara's Pattern

1st

2nd

3rd

4th

5th

6th

7th

3/8

5/16

9/32

17/64

33/128