an+a(n+1)+a(n+2)=37
a(n+1))+a(n+2))+a(n+3)=37
所以an=a(n+3)
a100=a1
2x=a9=a99=3-x => x=1
a3=a9=2x=2
a1=37-a2-a3=10
a100=10