a(n) = floor((sqrt(2) + sqrt(3))^n).

Terms

a(0) =1a(1) =3a(2) =9a(3) =31a(4) =97a(5) =308a(6) =969a(7) =3051a(8) =9601a(9) =30210a(10) =95049a(11) =299052a(12) =940897a(13) =2960313a(14) =9313929a(15) =29304086a(16) =92198401a(17) =290080547a(18) =912670089a(19) =2871501385a(20) =9034502497a(21) =28424933309a(22) =89432354889a(23) =281377831710a(24) =885289046401