# confusion on legendre symbol

i know that $\left(\frac{1}{2}\right)=1$ since $1^2\equiv 1 \pmod2$ now since $3\equiv 1\pmod2$ we should have $\left(\frac{3}{2}\right)=\left(\frac{1}{2}\right)=1$ but on Maple i get that $\left(\frac{3}{2}\right)=-1$ why?

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The command `\pmod` produces the appropriate spacing and font for this. – joriki Mar 2 '12 at 9:17

## 1 Answer

The Legendre symbol, the Jacobi symbol and the Kronecker symbol are successive generalizations that all share the same notation. The first two are usually only defined for odd lower arguments (primes in the first case), whereas the Kronecker symbol is also defined for even lower arguments.

Since the distinction is merely historic, I guess it makes sense for math software to treat them all the same; Wolfram|Alpha returns $-1$ for `JacobiSymbol(3,2)`. See the Wikipedia article for the definition for even lower arguments; the interpretation that a value of $-1$ indicates a quadratic non-residue is no longer valid in this case.

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