1|4+1|28+1|70+1|130+1|208+1|304
问题描述：
1|4+1|28+1|70+1|130+1|208+1|304
答
=(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)/3
=(1-1/16)/3
=5/16
答
1/1*4+1/4*7+1/7*10+1/10*13+.
1/3(1-1/4+1/4-1/7+.+1/16-1/19)
=1/3*18/19
=6/19