a(n) = 3*9^n + 8.

Terms

a(0) =11a(1) =35a(2) =251a(3) =2195a(4) =19691a(5) =177155a(6) =1594331a(7) =14348915a(8) =129140171a(9) =1162261475a(10) =10460353211a(11) =94143178835a(12) =847288609451