can you explain how to use a sequence like how to plug in numbers to the sequence

\(a_n=n\)

is the formula

Its like a is 0  so n=n 

15=15 

16=16 etc..

 The formula a_n=n says that "a" which is a term, n identify which term it is, so first term we would write it  as a_1 = As the sequence says 

here we see that a_1=1 and so on for a_15=15 

so we can make a general formula (Explicit) which is a_n=n for n is any number.