%I #9 Mar 13 2022 19:32:29
%S 1,2,4,9,21,59,162,483,1453,4492,14048,44616,142936,462380,1506534,
%T 4941955,16303783,54066560,180111432,602481589,2022797529,6814336663,
%U 23026359634,78027238290,265085903996,902733374480,3080967048004,10536594982790,36102498293396,123920278459564
%N Number of necklaces with n black and n white beads that avoid the pattern BBBB.
%H Marko R. Riedel et al., <a href="https://math.stackexchange.com/questions/4376420/">Necklaces made of black and white beads</a>, Math StackExchange, Feb 2022.
%F a(n) = A003239(n) - A351363(n).
%Y Cf. A351359, A351357, A351358, A351359, A351360, A351361.
%K nonn
%O 1,2
%A _Marko Riedel_, Feb 08 2022