更新时间2022-03-19 21:07:38
A=1+1/2+1/3+1/4+……+1/16
A=1+1/2+(1/3+1/4)+(1/5+1/6+1/7+1/8)
=(1/9+1/10+1/11+1/12+1/13+1/14+1/15+1/16)
A>1+1/2+2*1/4+4*1/8+8*1/16
=1+1/2+1/2+1/2+1/2
=3
A<1+1/2+2*1/4+(1/3-1/4)+4*1/8+(1/5-1/8)*3+8*1/16+(1*9-1/16)*7
=3+(1/12+9/40+49/144)
<4
∵ 3<A<4,∴ [A]=3