怀旧

1 = 1*1
1+3 = 2*2
1+3+5 = 3*3
1+3+5+7 = 4*4
1+3+5+7+9 = 5*5

1 = 1*1*1
3+5 = 2*2*2
7+9+11 = 3*3*3
13+15+17+19 = 4*4*4