a1 University of Nottingham University Park Nottingham NG7 2RP
In this paper, for R a commutative ring, with identity, of characteristic p, we look at the group G(R) of formal power series with coefficients in R, of the form
and the group operation being substitution. The results obtained give the exponent of the quotient groups Gn(R) of this group, n.
(Received January 15 1990)