1/2 1
1/3 2/3 2
1/4 2/4 3/4 3
1/5 2/5/ 3/5 4/5 4
1/64 .63/64 63
等差数列,由于
1+2+...+n=1/2*(n+1)*n
n=63,2016倒数一下,结果就是57/64