化简(-2)^2n+1+2(-2)^2n

2^n/n*(n+1) [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n 化简(n+1)(n+2)(n+3) 化简[n^2+(n+1)^2]/n(n+1) 化简额 化简：1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4) n(n+1)(n+2)数列求和 n(n+1)(n+2)等于多少? 根号【（2n+1）/（n²+n）】平方-4/（n平方+n ）化简 阶乘(2n-1)!=（2n)!/(2^n*n! 计算：n(n+1)(n+2)(n+3)+1 lim[(n+3)/(n+1))]^(n-2) 【n无穷大】