(1+x^2+x^4)^2 = (1+x^2+x^4)(1+x^2+x^4)
= 1 + x^2 + x^4 + x^2 + x^4 + x^8 + x^4 + x^8 + x^16
= 1 + 2x^2 + 2x^4 + 2x^8 + x^16