If `a_(1)=-1 and a_(n)=(a_(n-1))/(n+2)` then the value of `a_(4)` is ____.

If a_(1)=2 and a_(n)-a_(n-1)=2n(n>=2), find the value of a_(1)+a_(2)+a_(3)+....+a_(20)

If a_(1) = 2 and a_(n) - a_(n-1) = 2n (n ge 2) , find the value of a_(1) + a_(2) + a_(3)+…+a_(20) .

If a_(1) = 2 and a_(n) - a_(n-1) = 2n (n ge 2) , find the value of a_(1) + a_(2) + a_(3)+…+a_(20) .

If a_(1) = 4 and a_(n + 1) = a_(n) + 4n for n gt= 1 , then the value of a_(100) is

If a_1 = 4 and a_(n+1) = a_(n) + 4n for n ge 1 , then the value of a_(100) is

If a_(1), a_(2) , a_(3),…,a _(n+1) are in A. P. then the value of (1)/(a _(1)a_(2))+(1)/(a_(2)a_(3))+(1)/(a_(3)a_(4))+...+(1)/(a_(n)a_(n+1)) is-

Let (1 + x)^(n) = 1 + a_(1)x + a_(2)x^(2) + ... + a_(n)x^(n) . If a_(1),a_(2) and a_(3) are in A.P., then the value of n is

Let (1+x)^(n) = 1+a_(1)x + a_(2)x^(2) + ……+ a_(n)x^(n) . If a_(1), a_(2) and a_(3) are in AP, then the value of n is

If a_(n+1)=(1)/(1-a_(n)) for n>=1 and a_(3)=a_(1) then find the value of (a_(2001))^(2001)