`nth` term o f `1+ (1+2) + (1+2+3)+.................. (1+2+3+...+n)` is

nth term of 1+(1+2)+(1+2+3)+..............(1+2+3+...+n) is

nth term of the series 1,(1)/(2),(1)/(3),... is

The nth term of the given sequence 3/ (1^ 2) ⋅ 5/ (1^ 2 + 2^ 2) ⋅ 7/ (1^ 2 + 2^ 2 + 3^ 2) ⋅ 9/ (1^ 2 + 2^ 2 + 3^ 2 + 4^ 2)

If alpha is the nth root of unity then 1+2alpha+3alpha^(2)+ ............to n terms is equal to

If alpha (!=1) is a nth root of unity then S = 1 + 3alpha+ 5alpha^2 + .......... upto n terms is equal to

If alpha (!=1) is a nth root of unity then S = 1 + 3alpha+ 5alpha^2 + .......... upto n terms is equal to

If alpha (!=1) is a nth root of unity then S = 1 + 3alpha+ 5alpha^2 + .......... upto n terms is equal to