Number of 4-ary Lyndon words of length n with trace 0 mod 4.

Terms

a(0) =1a(1) =1a(2) =5a(3) =14a(4) =51a(5) =165a(6) =585a(7) =2032a(8) =7280a(9) =26163a(10) =95325a(11) =349350a(12) =1290555a(13) =4792905a(14) =17895679a(15) =67106816a(16) =252645135a(17) =954429840a(18) =3616814565a(19) =13743869130a(20) =52357696365a(21) =199911109725a(22) =764877654105