考虑数列 {bn}:
bn= an-2a'n+1' ,n=1,2,...2012;
b2013 = a2013 -2a1
设{an}前n项的和为Sn ,{bn}前n项的和为Tn
T2013 = S2013 - 2S2013 =0
又 |bn| = |b1| = p (p不小于0) n=1,2,...2013
下面用反证法证明p=0 .
若p非0 ,则p>0 ,bn各项均非0.
设 {bn}前2013项中正项项数为 k1,负项项数为k2 ,有k1+k2 =2013
0= T2013 = k1*p -k2*p =(k1-k2)p =(2013-2k2)p
由于(2013-2k2)是奇数减偶数结果非0,故上式与p非0矛盾
所以 p=0
bn=0 ,n=1,2,...2013
由 b2013 = a2013 -2a1=0 得 a2013 =2a1
由 bn= an-2a'n+1'=0 ,n=1,2,...2012;
得 a1 =2a2=4a3=...=[2^(2012)] a2013
所以 a1= 2^(2012)] 2a1 = 2^(2013)] a1
a1 =0 ,a2013=0
由 an =2a'n+1' ( n=1,2,...2012)得 an=0 ( n=1,2,...2013)
所以 a1=a2=...=a2013 =0