What is the way of integer representation of an element in $GF(3^{15})$
For each integer $i$ there is an polynomial representation in $GF(3^{15})$ by
for i in srange(F.cardinality()):
print(i, '=>', F(i.digits(3)))
As for example $4 \implies x + 1$. What is the reverses way that is, $ x + 1\implies 4$