a(n) = 5*a(n-2) + 2*a(n-3).

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =24a(5) =68a(6) =144a(7) =388a(8) =856a(9) =2228a(10) =5056a(11) =12852a(12) =29736a(13) =74372a(14) =174384a(15) =431332a(16) =1020664a(17) =2505428a(18) =5965984a(19) =14568468a(20) =34840776a(21) =84774308a(22) =203340816a(23) =493553092a(24) =1186252696a(25) =2874447092a(26) =6918369664a(27) =16744740852a(28) =40340742504a(29) =97560443588