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