How many terms are in the arithmetic sequence 1313, 1616, 1919, ..., 7070, 7373?

The formula in getting the arithmetic sequence:

an = a1 + (n - 1) d.

We can substitute the values in order for us to know how many terms the sequence has.

an = 7373

a1 = 1313

d = 303

an = a1 + (n - 1) d

7373 = 1313 + (n-1) 303

7373 = 1313 + 303n - 303

-303n = 1313 - 303 - 7373

303n = - 1313 + 303 + 7373

303n = 6363

n = 21

So, there are 21 terms in the sequence given.