为什么a1+2a2+2^2a3+...+2^(n-2)a(n-1)+2^(n-1)an=n^2 推得a1+2a2+2^2
已知数列{an}满足a1+a2+a3+...+an=n^2+2n.(1)求a1,a2,a3,a4
已知数列{an}中满足a1=1,a(n+1)=2an+1 (n∈N*),证明a1/a2+a2/a3+…+an/a(n+1
设数列{an}满足a1+2a2+3a3+.+nan=n(n+1)(n+2)
(a1+a2+a3+.+an)^2=a1^2+a2^2+.+an^2+2(a1a2+a2a3+...+a(n-1)an)
整数数列{An}满足 A1*A2+A2*A3+…+A(n-1)*An=(n-1)*n*(n+1)/3 ,(n=2,3,…
已知数列{an}满足a1=1,an=a1 +1/2a2 +1/3a3 … +1/(n-1)a(n-1),(n>1,n∈N
已知数列{an}满足a1=1;an=a1+2a2+3a3+...+(n-1)a(n-1);
设数列{an}满足a1+3a2+3^2a3+.3^n-1×an=n/3,a∈N+.
数列{an}满足:1/a1+2/a2+3/a3+…+n/an=2n
数列an满足a1+2a2+3a3+...+nan=(n+1)(n+2) 求通项an
设a1,a2…an是1,2…,n的一个排列,求证1/2+2/3+..+(n-1)/n≤a1/a2+a2/a3+...+a
已知数列an的前n项和为Sn=n^2+2n,求和:1/(a1*a2)+1/(a2*a3)+...+1/(an*a(n+1