1/6+1/12+1/20+……+1/156

1/6+1/12+1/20+……+1/156
=1/2*3+1/3*4+1/4*5+....+1/12*13
=(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+.....+(1/12-1/13)
=1/2-1/3+1/3-1&