//This shows that the primitive 9th division polynomial has irreducible factors of degree 9 and 27.

P<x>:=PolynomialRing(RationalField());
E:= EllipticCurve([0,0,0,0,4]);

f3:= DivisionPolynomial(E,3);
f9:= DivisionPolynomial(E,9);

f:=f9 div f3;
Factorisation(f);