Recursive and Explicit Sequence Rules

In recursive formulas what does the term a_n-1 represent?

In recursive formulas what does the term a₁ represent?

Write a recursive formula for the sequence 17,13,9,5...

Which sequence can be found using the recursive formula a₁=6, a_n= 4a_n-1, n>2

Use the explicit formula to find the 7th term of the sequence.
$$a_n=22-3\left(n-1\right)$$  

Use the explicit formula to find the 5th term of the sequence.
$$a_n=3\cdot2^{\left(n-1\right)}$$  

Find the first four terms of the sequence.

a_n= 3(4)ⁿ

Find $$a_4$$  for the sequence 2, 9, 16, 23, 30,...

Find the first four terms of the sequence.

a_n= 7(n + 2)