On the Multiplicative Order of an Modulo n
Jonathan Chappelon
Université Lille Nord de France
F-59000 Lille
France
Abstract:
Let n be a positive integer and αn be
the arithmetic function which assigns the multiplicative order of
an modulo n to every integer a
coprime to n and vanishes elsewhere.
Similarly, let βn assign
the projective multiplicative order of
an modulo n to every
integer a coprime to n and vanishes elsewhere. In this paper, we
present a study of these two arithmetic functions. In particular, we
prove that for positive integers n1 and
n2 with the same
square-free part, there exists a relationship between the functions
αn1 and
αn2
and between the functions
βn1 and
βn2.
This allows us to reduce the
determination of
αn
and
βn
to the case where n is
square-free. These arithmetic functions recently appeared in the
context of an old problem of Molluzzo, and more precisely in the study
of which arithmetic progressions yield a balanced Steinhaus triangle in
Z/nZ for n odd.
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Received October 16 2009;
revised version received January 20 2010.
Published in Journal of Integer Sequences, January 27 2010.
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