2013-2014 Fall OMO #3
Source:
October 30, 2013
Online Math Open
Problem Statement
A palindromic table is a array of letters such that the words in each row and column read the same forwards and backwards. An example of such a table is shown below.
\begin{array}[h]{ccc}
O & M & O \\
N & M & N \\
O & M & O
\end{array}
How many palindromic tables are there that use only the letters and ? (The table may contain only a single letter.)Proposed by Evan Chen