reversion of formal power series
formal power series
(optional) formal power series
The function reversion(a, b) returns the formal power series that is the reversion of a with respect to b. If b is not specified then it is assumed to be the formal power series with one nonzero coefficient, b⁡1=1.
Since reversion is the inverse of composition, composition of the result into a will give b.
Note that a⁡0 must be 0, a⁡1 must be 1, and b⁡0 must be 0. If not, the reversion is not well defined and reversion returns an error message.
The command with(powseries,reversion) allows the use of the abbreviated form of this command.
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