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

Terms

a(0) =0a(1) =1a(2) =3a(3) =6a(4) =21a(5) =81a(6) =252a(7) =729a(8) =2187a(9) =6642a(10) =19845a(11) =59049a(12) =176904a(13) =531441a(14) =1594323a(15) =4780782a(16) =14344533a(17) =43046721a(18) =129146724a(19) =387420489a(20) =1162261467a(21) =3486843450a(22) =10460471301a(23) =31381059609a(24) =94143001680a(25) =282429536481a(26) =847288609443