  A palstar (after Knuth, Morris, and Pratt) is a concatenation of even-length
palindromes. We show that, asymptotically, there are $\Theta(\alpha_k^n)$
palstars of length $2n$ over a $k$-letter alphabet, where $\alpha_k$ is a
constant such that $2k-1 < \alpha_k < 2k-{1 \over 2}$. In particular, $\alpha_2
\doteq 3.33513193$.
