a = 11
b = 16 (or vice versa)

11 and 16 both are greater than 1
11 and 16 are not equal

a^2 + 3b = 11^2 + 3*16 = 121+48 = 169
b^2 + 3a = 16^2 + 3*11 = 256+33 = 289

169 and 289 are perfect squares of 13 and 17 resp