Infinity symbol in bookbinding to indicate that a book is printed on acid-free paper and will therefore be long-lasting. In modern mysticism, the infinity symbol has become identified with a variation of the ouroboros, an ancient image of a snake eating its own tail that has also come to symbolize the infinite, and the ouroboros is sometimes drawn in figure-eight form to reflect this identification, rather than in its more traditional circular form. In the works of Vladimir Nabokov, including "The Gift" and "Pale Fire", the figure-eight shape is used symbolically to refer to the Möbius strip and the infinite, for instance
Legendre symbol alternative expressions for the Legendre symbol were devised in order to produce various proofs of the quadratic reciprocity law. The above properties, including the law of quadratic reciprocity, can be used to evaluate any Legendre symbol. For example: Or using a more efficient computation: The article Jacobi symbol has more examples of Legendre symbol manipulation. Legendre symbol In number theory, the Legendre symbol is a multiplicative function with values 1, −1, 0 that is a quadratic character modulo an odd prime number "p": its value on a (nonzero) quadratic residue mod "p" is 1 and on a non-quadratic residue ("non-residue")