2/3*5+1/5*7+1/7*9+1/9*11+1/11*13
=1/15+1/2(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)
=1/15+1/2(1/3-1/13)
=38/195