14/06/17 00:37:55.27
>>136
1+1/2+1/3+…+1/(4m-1)-2(1/2+1/4+1/6+…1/(4m-2))
=1+1/2+1/3+…+1/(4m-1)+(1+1/2+1/3+…1/(2m-1))
=1/(2m)+1/(2m+1)+1/(2m+2)+…+1/(4m-3)+1/(4m-2)+1/(4m-1)
=1/(2m)+1/(4m-1) + 1/(2m+1)+1/(4m-2) + 1/(2m+2)+1/(4m-3) + … + 1/(3m-1)+1/(3m)
=(6m-1)/((2m)(4m-1)) + (6m-1)/((2m+1)(4m-2) + (6m-1)/((2m+1)(4m-3) + … (6m-1)/(3m-1)(3m)
6m-1が素数なので、分子は6m-1を因数にもつ。