Magick

Take a magic square. You have the rules that all the rows and columns add up to some constant. Normally a restriction is also imposed on the diagonal sums. For purposes of ease of manipulation, let that constant (also known as the magic constant) be 0. We’re going to ignore the restriction that the square [...]

;colours

Blah blah blah chromatic numbers of graphs. This one isn’t too hard to prove. Given a -colouring of , group the vertices by colour, then since the vertices with the same colour induce a null subgraph of (correspondingly, a complete subgraph of ), is at least the size of the largest group of vertices, which [...]