There is already a derived formula for this type of series. This is arithmetic series. It consists of a group of numbers arranged to together with a common difference. For this series, the common difference is 2. See the pattern: 4-2 = 2, 6 - 4 = 2, 8 - 6 = 2, 10- 8=2
The formula for an arithmetic series is
An = A1 + (n-1)d
where An is the nth term of the series, A1 is the 1st term, n is the number of terms and d is the common difference.
