1/1*7+1/7*13+1/13*19+~~~+1/97*103
=(6/1*7+6/7*13+6/13*19+~~~+6/97*103)/6
=[(1/1-1/7)+(1/7-1/13)+(1/13-1/19)+~~~+(1/97-1/103)]/6
=(1-1/103)/6
=17/103