Sn=((An+1)/2)^2
A1=S1=((A1+1)/2)^2
(A1-1)^2=0
A1=1
Sn=n(A1+An)/2=n(1+An)/2=((An+1)/2)^2
(An+1)/2=n
An=2n-1
Sn=n(1+2n-1)/2=n^2
Bn=(-1)^n×Sn=(-1)^n×Sn^2
如果n為偶數(shù)
設(shè)C(n/2)=B(n-1)+Bn=-(n-1)^2+n^2=2n-1
Cn=4n-1
Mn是{Cn}前n項(xiàng)和
Mn=(3+4n-1)n/2=n(2n+1)
Tn=M(n/2)=n(n+1)/2
如果n為奇數(shù)
C((n+1)/2)=Bn+B(n+1)=-n^2+(n+1)^2=2n+1
Cn=4n-1
Mn=n(2n+1)
Tn=M((n-1)/2)+Bn=(n-1)/2×(2(n-1)/2+1)-n^2=-n(n+1)/2