First 5 terms in a number sequence 0.5 1 2 4 8

A) write down the term to term rule

b) 7th term of sequence

c) why cant 1527 be a term of the sequence

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236