An improved lower bound on the covering number K2(9, 1) Original Research Article

In this article we improve the lower bound for K2(9, 1), the minimum cardinality of a binary code of length 9 and covering radius 1. We show that a binary code of length 9, 55 codewords and covering radius 1 does not exist which gives a new lower bound K2(9, 1) ⩾ 56.