Number of strings over Z_3 of length n with trace 1 and subtrace 0.

Terms

a(0) =1a(1) =2a(2) =3a(3) =9a(4) =30a(5) =81a(6) =225a(7) =702a(8) =2187a(9) =6561a(10) =19602a(11) =59049a(12) =177633a(13) =532170a(14) =1594323a(15) =4782969a(16) =14351094a(17) =43046721a(18) =129127041a(19) =387400806a(20) =1162261467a(21) =3486784401a(22) =10460294154a(23) =31381059609a(24) =94143533121a(25) =282430067922a(26) =847288609443