a(0) = 16, a(n+1) = 3a(n) - (6-n)^2.

Terms

a(0) =16a(1) =12a(2) =11a(3) =17a(4) =42a(5) =122a(6) =365a(7) =1095a(8) =3284a(9) =9848a(10) =29535a(11) =88589a(12) =265742a(13) =797190a(14) =2391521a(15) =7174499a(16) =21523416a(17) =64570148a(18) =193710323a(19) =581130825a(20) =1743392306a(21) =5230176722a(22) =15690529941a(23) =47071589567a(24) =141214768412