Suppose that n ε and a = (a0, …, an − 1) is a sequence of length n with ai ε {0, 1}. For 0 k n − 1, let We call the sequence avery odd if Ak is odd for 0 k n − 1. We prove that there are very odd sequences of length n> 1 if and only if the order of 2 is odd in the multiplicative group of integers modulo 2n − 1.