%N Numbers k such that a Golay sequence of length k exists.
%C It is known that the sequence contains all numbers 2^i 10^j 26^m, and that all terms k > 1 are even and not divisible by any prime == 3 (mod 4). But the full characterization of these numbers is an open problem.
%H Dragomir Z. Dokovic, <a href="http://dx.doi.org/10.1016/S0012-365X(98)00034-X">Equivalence classes and representatives of Golay sequences</a>, Discrete Math. 189 (1998), no. 1-3, 79-93. MR1637705 (99j:94031).
%Y Cf. A208924-A208929.
%A _N. J. A. Sloane_, Mar 02 2012