MathDB
2016 Guts #21

Source:

August 14, 2022
2016Guts Round

Problem Statement

Suppose that we have a 2×52\times5 grid, and we wish to write 00's and 11's inside such that for any 2×22\times2 sub-block, the <spanclass=latexitalic>determinant</span><span class='latex-italic'>determinant</span> is 00. The determinant of a 2×22\times2 block [abcd]\textstyle\begin{bmatrix}a&b\\c&d\end{bmatrix} is adbcad-bc. For example, the following is a valid configuration: However, the following is not valid because the last 2×22\times2 sub-block has determinant 11: How many such valid 2×52\times5 configurations are there?