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

Terms

a(0) =3a(1) =2a(2) =4a(3) =11a(4) =24a(5) =52a(6) =115a(7) =254a(8) =560a(9) =1235a(10) =2724a(11) =6008a(12) =13251a(13) =29226a(14) =64460a(15) =142171a(16) =313568a(17) =691596a(18) =1525363a(19) =3364294a(20) =7420184a(21) =16365731a(22) =36095756a(23) =79611696a(24) =175589123a(25) =387274002a(26) =854159700a(27) =1883908523a(28) =4155091048a(29) =9164341796