Sum the following series to `n` terms: `4+6+9+13+18+`

Explanation

Given,

`4 + 6 + 9 + 13 + 18 +.... `

The differences between the
successive terms is `2, 3, 4, 5+... `which is an A.P. with common difference 1.



Let `T_n= n^(th)` term

and

`S_n =` sum of n terms of the given series.
Then,
`S_n=4+6+13+18...T_(n−1)+T_n...(i)`
...