a(n) = 3*a(n-1) - 2*a(n-2) + 5*a(n-3) starting with 1, 2, 3.

Terms

a(0) =1a(1) =2a(2) =3a(3) =10a(4) =34a(5) =97a(6) =273a(7) =795a(8) =2324a(9) =6747a(10) =19568a(11) =56830a(12) =165089a(13) =479447a(14) =1392313a(15) =4043490a(16) =11743079a(17) =34103822a(18) =99042758a(19) =287636025a(20) =835341669a(21) =2425966747a(22) =7045397028a(23) =20460965935a(24) =59421937484a(25) =172570865722a(26) =501173551873