a(n) = 2*a(n-1) + 3*a(n-2), a(0) = 1, a(1) = 4.

Terms

a(0) =1a(1) =4a(2) =11a(3) =34a(4) =101a(5) =304a(6) =911a(7) =2734a(8) =8201a(9) =24604a(10) =73811a(11) =221434a(12) =664301a(13) =1992904a(14) =5978711a(15) =17936134a(16) =53808401a(17) =161425204a(18) =484275611a(19) =1452826834a(20) =4358480501a(21) =13075441504a(22) =39226324511a(23) =117678973534a(24) =353036920601