Let $ k$ be an even number. For a $ k$ -dimensional cube (http://mathworld.wolfram.com/HypercubeGraph.html) $ Q_k$ , let $ G$ be a subgraph of $ Q_k$ with $ 2^{k-1}+s$ vertices, for $ 1\le s\le 2^{k-1}-1$ . I am wondering what is maximum number of edges $ G$ can have? A theorem says average degree ofRead more