Smooth Lyndon words with 4 colors.

Terms

a(0) =1a(1) =4a(2) =3a(3) =8a(4) =18a(5) =47a(6) =108a(7) =268a(8) =638a(9) =1553a(10) =3761a(11) =9189a(12) =22453a(13) =55185a(14) =135894a(15) =335906a(16) =832312a(17) =2068066a(18) =5149845a(19) =12852750a(20) =32138353a(21) =80509495a(22) =202013368a(23) =507669048a(24) =1277586867a(25) =3219366610a(26) =8122275225