Number of step cyclic shifted sequences using exactly three different symbols.

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =9a(5) =56a(6) =51a(7) =258a(8) =380a(9) =1500a(10) =1611a(11) =12298a(12) =10245a(13) =57108a(14) =121721a(15) =346146a(16) =474489a(17) =3589534a(18) =3397143a(19) =21984804a(20) =41570773a(21) =142619388a(22) =186027579a(23) =1476414178a(24) =1694455320a(25) =8146633638a(26) =15690141155