## Riordan group involutions.(English)Zbl 1131.05012

Summary: We study involutions in the Riordan group, especially those with combinatorial meaning. We give a new determinantal criterion for a matrix to be a Riordan involution and examine several classes of examples. A complete characterization of involutions in the Appell subgroup is developed. In another direction we find several examples that generalize the RNA matrix but are of independent interest.

### MSC:

 05A30 $$q$$-calculus and related topics 05A15 Exact enumeration problems, generating functions 05B20 Combinatorial aspects of matrices (incidence, Hadamard, etc.)
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### References:

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