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

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =6a(5) =20a(6) =14a(7) =48a(8) =52a(9) =140a(10) =108a(11) =624a(12) =352a(13) =1400a(14) =2172a(15) =4464a(16) =4116a(17) =22112a(18) =14602a(19) =68016a(20) =88376a(21) =209936a(22) =190746a(23) =1075200a(24) =839128a(25) =2797000a(26) =3730584a(27) =11276704a(28) =9587580a(29) =67195520