## Residue multiplication table

mulres version 0.1 (c) Brian Chandler 1993

This prints the multiplication table of the residues modulo n which
are coprime to n. (In other words, multiplication round the "number
circle of size n" in place of the ordinary "number line" of integers.)

The function φ(n) (also known as Euler's totient function) is defined as the number of these residues.
Moreover, the residues form a group under multiplication, as you
can check from the table: associativity is obvious, since
multiplication in the integers is associative, multiplication is
closed, since if you multiply together two numbers coprime to n,
the answer must also be coprime, and um inverses are established
by a bit of hand waving (the cancellation laws work, for a start).

coprime: argument must be number

coprime: argument must be positive

Modulus:

Group of coprime residues modulo under multiplicationn