Find the sum to n terms of the series (1)+(1+a)+(1+a+`a^(2)) cdots`.

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

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

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

Find the sum to n terms of the series , (1)/(1.2)+(1)/(2.3)+(1)/(3.4)+.... ?

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

The sum to n term of the series 1(1!)+2(2!)+3(3!)+

The sum to n term of the series 1(1!)+2(2!)+3(3!)+

If S denotes the sum to infinity and S_(n) , denotes the sum of n terms of the series 1+(1)/(2)+(1)/(4) + (1)/(8)+ cdots , such that S-S_(n) lt (1)/(100) , then the least value of n is

Find the sum to n terms of the series 4+41+401+4001+ cdots