a1=3/5,an=1-1/a(n-1)a2=1-1/(3/5)=-2/3a3=1+3/2=5/2a4=1-2/5=3/5=a1 a5=-2/3=a2a6=a3=5/2所以a(3*正整数倍)=a3=5/2所以a2010=a(670*3)=5/2a2011=1-1/a2010=1-1/(3/5)=-2/3