Observe the following formula and fill in the numbers regularly 1+2+1= 1+2+3+2+1= 1+2+3+4+3+2+1= First question, four square squares, fill in the number The second question, nine square squares, fill in the number The third question, 16 square squares, fill in the number

Observe the following formula and fill in the numbers regularly 1+2+1= 1+2+3+2+1= 1+2+3+4+3+2+1= First question, four square squares, fill in the number The second question, nine square squares, fill in the number The third question, 16 square squares, fill in the number

n^2
Square of n