  We examine the series expansions of the solutions of the confluent Heun
equation in terms of three different sets of the Kummer confluent
hypergeometric functions. The coefficients of the expansions in general obey
three-term recurrence relations defining double-sided infinite series; however,
four-term and two-term relations are also possible in particular cases. The
conditions for left- and/or right-side termination of the derived series are
discussed.
