Theoretical Computer Science Cheat Sheet, created by Steve Seiden, is a hodgepodge of well-known mathematical theorems and notions.
I can understand (or guess at least) many of them, but I'm not sure about this 10-by-10 table at the end of the document. What is this matrix? The document has no explanation at all, and I'm wondering why the author put in a cheat sheet.
Is there any special meaning in computer science or math that this matrix stands for?
Arranging the integers from $0$ to $99$ in a $10\times10$ square in such a way that no two in the same row or column have the same first digit or the same second digit.
It can be seen as a pair of orthogonal latin squares of order $10$: the first digits form one square, the second digits the other.
Source: quick google search for the first row. See this PDF, 23.5.1.