Sum of `-2 , 2 1/2 , -3 1/8 . . . . `upto 6 terms is

sum-2,2(1)/(2),-3(1)/(8),...... to 6 terms

Sum of first 20 terms of 3/1^2 + 5/(1^2 + 2^2) + 7/(1^2 + 2^2 + 3^2) +... upto 20 terms is :

The value of i^2 + i^4 + i^6 + i^8.... upto (2n+1) terms , where i^2 = -1, is equal to:

The value of the sum 1.2.3+2.3.4+3.4.5+… upto n terms is equal to

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

sum-2,-2(1)/(2),-3(1)/(8),, to 6 terms.

1^(2) + 3^(2) + 5^(2) + …. upto n terms =