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

Terms

a(0) =2a(1) =4a(2) =6a(3) =12a(4) =12a(5) =40a(6) =28a(7) =96a(8) =104a(9) =280a(10) =216a(11) =1248a(12) =704a(13) =2800a(14) =4344a(15) =8928a(16) =8232a(17) =44224a(18) =29204a(19) =136032a(20) =176752a(21) =419872a(22) =381492a(23) =2150400a(24) =1678256a(25) =5594000a(26) =7461168a(27) =22553408a(28) =19175160a(29) =134391040