1²+2²+3³+…+n²的和∵(n+1)³-n³=3n²+3n+1∴n=1时有 2³-1³=3*1²+3*1+1n=2时有 3³-2³=3*2²+3*2+1n=3时有 4³-3³=3*3² +3*3+1.n=n时...