A note on 2‾-separable codes and B2 codes

We derive a simple proof, based on information theoretic inequalities, of an upper bound on the largest rates of q-ary 2‾-separable codes that improves recent results of Wang for any q≥13. For the case q=2, we recover a result of Lindström, but with a much simpler derivation. The method easily extends to give bounds on B2 codes which, although not improving on Wang's results, use much simpler tools and might be useful for future applications.