how to write an expression that can be used to find the nth

how to write an expression that can be used to find the nth term of each sequence?
numbers involved: 7,10,13,16,19,22,25

Solution

The sequence appears to increase by 3 with every term, starting with a1=7. There are two ways to write the n-th term of such a sequence:

The recursive way: an+1=an+3, a1=7, n=1,2,3,...

The explicit way: an=4+3n, n=1,2,3,...

Both ways are equally important.