First 100 terms of the following sequence 3 ,7 ,11

Comment
Quick 20100
I'm going to guess and say you want the sum of the first hundred terms of this series.

Givens
a1 = 3
n = 100
d = 4

Step One
Find L
L = a1 + (n - 1)*d
L = 3 + (100 - 1)*4
L = 3 +  99 * 4
L = 399

Step 2
Find the sum of the first 100 terms of the series.

Sum = (a + L)*n/2

Givens
a = 3
L = 399
n = 100

Sum = (3 + 399)*100/2
Sum = 402 * 50
Sum = 20100   <<<<< Answer

Please leave a note if I am incorrect.