If `a_n=n/((n+1)!)` then find `sum_(n=1)^50 a_n`

If a_n = n (n!) , then sum_(r=1)^100 a_r is equal to

If a_n=sin((npi)/6) then the value of sum _(n=2 )^6 a_n^2

a_n=(n-1)(n-2) then a_5 =….

If a_n=(n(n+1))/2 a_4 =…..

If a_n=sin((npi)/6) then the value of sum a_n^2

If a_n=sin((npi)/6) then the value of sum a_n^2

Let a_n is a positive term of a GP and sum_(n=1)^100 a_(2n + 1)= 200, sum_(n=1)^100 a_(2n) = 200 , find sum_(n=1)^200 a_(2n) = ?

Let a_n is a positive term of a GP and sum_(n=1)^100 a_(2n + 1)= 200, sum_(n=1)^100 a_(2n) = 200 , find sum_(n=1)^200 a_(2n) = ?

If a_n=sum_(r=0)^n1/(""^nC_r) , then sum_(r=0)^nr/(""^nC_r) equals :

If a_n=sum(r=0)^n 1/^nC_r, then sum _(r=0^n r/^nC_r equals (A) (n-1)a_n (B) na_n (C) 1/2na_n (D) none of these