數列的通項

1 x 1 = 1
2 x 2 = 4
3 x 3 = 9
4 x 4 = 16
5 x 5 = 25
n x n = n^2
SO the solution is n^2

1^2,2^2,3^2,4^2,5^2,................
=n^2

1,4,9,16,25
=1*1, 2*2, 3*3, 4*4, 5*5....
(or =1^2, 2^2, 3^2, 4^2, 5^2....)

即是n^2.