Kronecker symbol

The Kronecker symbol $\left({\frac {a}{2}}\right)$ is a function similar to the Legendre and Jacobi symbols.

It is defined thus:

• $\left({\frac {a}{2}}\right)=-1$ if $a\equiv 5\mod 8$
• $\left({\frac {a}{2}}\right)=0$ if $a\equiv 0\mod 4$
• $\left({\frac {a}{2}}\right)=1$ if $a\equiv 1\mod 8$

The symbol is undefined for singly even numbers.

See also: Kronecker delta.