  When a Catalan number or a Narayana number is a (non-trivial) perfect power?
For Catalan numbers, we show that the answer is "never". However, we prove that
for every b, the Narayana number N(a,b) is a (non-trivial) perfect square for
infinitely many values of a, and we show how to compute all of them. We also
conjecture that N(a,b) is never a (non-trivial) perfect k-th power for k
greater than 2 and we prove some cases of this conjecture.
