" The value of "sum_(r=1)^(15)(r.2)/((r+2)!)" is equal to "

The value of sum_(r=1)^(15) (r2^(r))/((r+2)!) is equal to

The value of sum_(r=1)^(15) (r2^(r))/((r+2)!) is equal to (a) ((17)!-2^(16))/((17)!) (b) ((18)!2^(17))/((18)!) (c) ((16)!-2^(15))/((16)!) (d) ((15)!-2^(14))/((15)!)

The value of sum_(r = 16)^(30)(r + 2)(r - 3) is equal to :

The value of sum_(r=1)^(oo)cot^(-1)(2r^(2)) is equal to

The value of sum_(r=0)^(n)r(n-r)(nC_(r))^(2) is equal to

The value of sum_(r=1)^(oo)(r)/(3^r) is equal to:

sum_(r=1)^(20)(r^2)/((r!(20-r)!)^(2)) is equal to

value of sum_(r=0)^(2n)rC(2n,r).((1)/(r+2)) is equal to:

sum_(r=1)^(n)(C(n,r))/(r+2) is equal to