SOLUTION: https://media.educationgalaxy.com/content/Images/Questions/doreen@educationgalaxy.com/image--480079904.jpg

S(1) = 1

S(2) = 3

S(3) = 6

S(4) = 10


The common term  S(n)  is the sum of the first "n" natural numbers


    S(n) = 1 + 2 + 3 + 4 + . . . + n.


It is WELL KNOWN fact that S(n) = .


ANSWER.  S(n) = .