1又3分之1+2又15分之1+3又35分之1+4又63分之1+5又99分之1=(1+2+3+4+5)+(1/3+1/15+1/35+1/63+1/99)=15+[1/(1*3)+1/(3*5)+1/(5*7)+1/(7*9)+1/(9*11)]=15+[1/1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11]/2=15+[1-1/11]/2=...