Number of strings over Z_3 of length n with trace 0 and subtrace 2.

Terms

a(0) =0a(1) =2a(2) =6a(3) =12a(4) =30a(5) =90a(6) =252a(7) =702a(8) =2106a(9) =6480a(10) =19602a(11) =58806a(12) =176904a(13) =532170a(14) =1596510a(15) =4785156a(16) =14351094a(17) =43053282a(18) =129146724a(19) =387400806a(20) =1162202418a(21) =3486725352a(22) =10460294154a(23) =31380882462a(24) =94143001680a(25) =282430067922a(26) =847290203766