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2019-03-05 14:13:50 -0600 | asked a question | Checking that symbolic expression is zero How do I show that a simple algebraic expression like e.g. is zero? |

2017-06-24 05:10:32 -0600 | commented answer | Elements in the lattice $A_n$ Sorry this uses the wrong norm. Actually the norm of the OP is not a norm. |

2017-06-24 05:10:32 -0600 | commented answer | Series expansion for theta function of even lattice Thanks a lot. I figured this in the meanwhile and wrote my own answer which i guess needed moderating. I definitely think the documentation should be updated. Or an example like $A_2$ should be given. |

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2017-06-22 08:33:56 -0600 | asked a question | Series expansion for theta function of even lattice I am new to sage and trying to figure out how to calculate the series expansion of the theta function for an even lattice $L$, i.e. $$\Theta_L(q)=\sum_{x\in L} q^{\langle x,x\rangle/2}$$ I tried the following code for the $A_2$ lattice, but I doesn't really do what its supposed to do Q=QuadraticForm(QQ,2,[2,-1,2]); Q Q.theta_series(20) I found the following code on https://oeis.org/A004016 (OEIS), which gives the correct result: ModularForms( Gamma1(3), 1, prec=81).0 |

2017-06-22 08:33:47 -0600 | answered a question | Elements in the lattice $A_n$ I would suggest something like this k=2 Q=QuadraticForm(ZZ,2,[1,-1,1]);Q m=Q.short_vector_list_up_to_length(k^2+1) m[k^2] which is $A_2$ for some $k$ which gives the result in the basis $e_1=(1,-1,0), e_2=(0,1,-1)$. |

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