Is it can be prove or disprove?

There exist positive integers m,n,where m,n and m n are all perfect squares?
some other possibilities:



m = 81 (9)

n = 144 (12)

m n = 225 (15)



m = 144 (12)

n = 256 (16)

m n = 400 (20)



m = 225 (15)

n = 400 (20)

m n = 625 (25)



In general: (3a), (4a), and (3a) (4a), where a = 1, 2, 3, ...
m=36(6^2)

n=64(8^2)

m n=100(10^2)
m=9

n=16

m n=25



Edit: Beaten to it. Both answers are correct.