Find the sum of the series `1+ (1+2) + (1+2+3) + (1+2 + 3 +4)+ … + (1+2+3+… + 20)`.

Sum to n terms the series 1 + (1+ 2) + (1 + 2 + 3) + (1 + 2 + 3 + 4).......

Find the sum of the infinite series. 1/(1.2)+1/(2.3)+1/(3.4)+...

Find the sum to n terms of the series 1/(1 + 1^2 + 1^4) + 2/(1 + 2^2 + 2^4) + 3/(1 + 3^2 + 3^4) + ...

Sum of the series S = 1 + (1)/(2)(1 + 2) + (1)/(3) ( 1 + 2 + 3 ) + (1)/(4) ( 1 + 2 + 3 + 4 ) + …… upto 20 terms is