Number of ways to choose 2^n vectors in {0, 1, 2, 3}^n such that any two differ by at least 2 in at least one coordinate (2^n being maximal).

A011187

Number of ways to choose 2^n vectors in {0, 1, 2, 3}^n such that any two differ by at least 2 in at least one coordinate (2^n being maximal).