Equazioni caratteristiche per la commutativitÓ
Received: 15 July 1993
AMS Classification : 03B99
Abstract Let f be a binary operation on the positive integers obtained by primitive recursion from g and φ ; in a preceeding work ( see  we gave a sufficient condition on g and φ for f to be commutative. Here, after disproving the necessity of that condition, we give a set of equations of the defining functions whose satisfaction is both necessary and sufficient for the commutativity of the function to be defined.