" (vi) "1+2+3+cdots+n<(1)/(8)(2n+1)^(2)1=

Find the sum 1+(1)/(1+2) + (1)/(1+2+3) + cdots+ (1)/(1+2+3+cdots+ n )

Let P(x) =a_(0)+a_(1)x^2+a_(2)x^(4)+cdots+a_(n)x^(2n) with all a_(i) gt0 , i=0,1,2,3, cdots ,n . Then P(x) has

The mean of the squares of the numbers 1,2,3,4, cdots n is

If (1.2+2.3+3.4+cdots "to n terms")/(1+2+3+cdots "to n terms") =6 find n.

If H_(n) =1+(1)/(2)+ cdots + (1)/(n) then value of S_(n) =1 + (3)/(2) + (5)/(3) +cdots + (2n-1)/(n) is

Find the sum of the series 1.n + 2 .(n-1) + 3.(n-2) + cdots + ( n-1) .2 + n.1.

If a_(1) , a_(2), a_(3) , cdots ,a_(n) are in A.P. with a_(1) =3, a_(n) =39 and a_(1) +a_(2) + cdots +a_(n) =210 then the value of n is equal to