a(n) = a(n-1) + 3*a(n-2) with n>1, a(0)=1, a(1)=6.

Terms

a(0) =1a(1) =6a(2) =9a(3) =27a(4) =54a(5) =135a(6) =297a(7) =702a(8) =1593a(9) =3699a(10) =8478a(11) =19575a(12) =45009a(13) =103734a(14) =238761a(15) =549963a(16) =1266246a(17) =2916135a(18) =6714873a(19) =15463278a(20) =35607897a(21) =81997731a(22) =188821422a(23) =434814615a(24) =1001278881a(25) =2305722726a(26) =5309559369a(27) =12226727547a(28) =28155405654a(29) =64835588295