Number of strings over Z_3 of length n with trace 1 and subtrace 2.

Terms

a(0) =0a(1) =0a(2) =3a(3) =12a(4) =30a(5) =81a(6) =252a(7) =756a(8) =2187a(9) =6480a(10) =19602a(11) =59049a(12) =176904a(13) =530712a(14) =1594323a(15) =4785156a(16) =14351094a(17) =43046721a(18) =129146724a(19) =387440172a(20) =1162261467a(21) =3486725352a(22) =10460294154a(23) =31381059609a(24) =94143001680a(25) =282429005040a(26) =847288609443