To prove that a2016>21+a1000, we need to analyze the given sequence and its properties.
1. Define the sequence and initial condition:
a1=0
an+1=na1+a2+…+an+1
2. Calculate the first few terms to identify a pattern:
a2=1a1+1=0+1=1
a3=2a1+a2+1=20+1+1=21+1=23
a4=3a1+a2+a3+1=30+1+23+1=325+1=65+1=611
3. Generalize the sequence:
Notice that the sequence an can be expressed in terms of the harmonic series. We can rewrite the recurrence relation as:
Sn=a1+a2+…+an
an+1=nSn+1
Sn+1=Sn+an+1=Sn+nSn+1=Sn(1+n1)+1
Sn+1=Snnn+1+1
4. **Simplify the sum Sn:**
Sn+1=Snnn+1+1
Sn+1=Sn(1+n1)+1
By induction, we can show that Sn grows approximately as nlogn.
5. **Estimate an:**
Since an=n−1Sn−1+1, we can approximate:
an≈logn+1
6. **Compare a2016 and a1000:**
a2016≈log2016+1
a1000≈log1000+1
log2016≈log(2×1008)≈log2+log1008≈0.301+log1000+log1.008
log1000=3,log1.008≈0.003
log2016≈0.301+3+0.003=3.304
a2016≈3.304+1=4.304
a1000≈3+1=4
21+a1000=21+4=4.5
7. Conclusion:
a2016≈4.304<4.5
Therefore, the inequality a2016>21+a1000 does not hold.
The final answer is a2016<21+a1000