Let $E:y^2=x^3+x/\Bbb{Q}_7(\sqrt{-1})$ be an elliptic curve. Let $ \hat E$ be a formal group of $E$.
I want to prove $[7](t)≡t^{49}mod7\Bbb{Z}_7$ does not hold, so indeed I want to know the coeffients of $t^{49},t^{50},t^{51},・・,$ but this is impossible with hand calculation.
But I'm not familiar with computer calculating. I want to be able to use computer, but result only is ok here, thank you for your help.
Calculating $[7](t)$ polynomial of elliptic curve with computer
algebraic-number-theorycomputational mathematicselliptic-curvessagemath
Best Answer
Working over $\Bbb F_7$, the field with seven elements, sage gives:
Over $\Bbb Q$ the result is not so simply displayed, i will adjust manually:
And indeed, the coefficient in $t^{49}$ is $-1$ modulo seven:
Later comment: One can reproduce the same also in pari/gp. See also:
MO related question
Code:
And after copy+paste into the pari interpreter:
And pari gives the result almost instantly. (In sage we may need some coffee in between, and there is no problem if we have to buy it first next corner.)