By extending both arithmetical operations into finite sets of natural numbers, from the entire set of natural numbers successively deleting some residue classes
In two previous papers, we explained the classification of all crystallographic point groups of n-dimensional space with n ≤ 6 into different isomorphism class
Starting from general Jacobi polynomials we derive for the Ul-traspherical polynomials as their special case a set of related polynomials which can be extended