（1/8+1/24+1/48+1/80+1/120+1/168+1/224+1/288)×128=128×(1/8)[1+1/3+1/6+1/10+1/15+1/21+1/28+1/36] =128×(1/8)[1+2(1/(2×3)+1/(3×4)+1/(4×5)+1/(5×6)+1/(6×7)+1/(7×8)+1/(8×9)] =128×(1/8)[1+2(1/2-1/...