Find the sum of n terms of the series.
`sqrt(7) + sqrt(21) +3sqrt(7)+……….`

Find the sum of the first n terms of the series: 3+7+13 +21 +31 +...

Find the sum of n terms of the following series : 1+3+7+13 +......

Sum to n terms the series 1+3+5+7+9+...

Find the nth term and the sum of n terms of the series : 6 +9 +21 + 69 + 261 + ....

Find the sum to n terms of the series given below:- 5^2 + 6^2 + 7^2 + ... + 20^2

Find the sum upto n terms of the series 1+4+7+10+13+16+"...." .

Find the sum of n terms of the following series : 7+77+777 +......

Find the sum to n terms of the series (1)/(1*3*5*7*9)+(1)/(3*5*7*9*11)+(1)/(5*7*9*11*13)+"......" . Also, find the sum to infinty terms.

Find the sum of n terms of the following series : 1+3+7+15+31 +......