Number of step shifted (decimated) sequence structures using exactly two different symbols.

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =5a(5) =19a(6) =13a(7) =47a(8) =51a(9) =139a(10) =107a(11) =623a(12) =351a(13) =1399a(14) =2171a(15) =4463a(16) =4115a(17) =22111a(18) =14601a(19) =68015a(20) =88375a(21) =209935a(22) =190745a(23) =1075199a(24) =839127a(25) =2796999a(26) =3730583a(27) =11276703a(28) =9587579a(29) =67195519