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

Terms

a(0) =0a(1) =2a(2) =4a(3) =10a(4) =10a(5) =38a(6) =26a(7) =94a(8) =102a(9) =278a(10) =214a(11) =1246a(12) =702a(13) =2798a(14) =4342a(15) =8926a(16) =8230a(17) =44222a(18) =29202a(19) =136030a(20) =176750a(21) =419870a(22) =381490a(23) =2150398a(24) =1678254a(25) =5593998a(26) =7461166a(27) =22553406a(28) =19175158a(29) =134391038