a(n) = 5*a(n-2) - 2*a(n-4), with initial terms 0,1,1,3.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =5a(5) =13a(6) =23a(7) =59a(8) =105a(9) =269a(10) =479a(11) =1227a(12) =2185a(13) =5597a(14) =9967a(15) =25531a(16) =45465a(17) =116461a(18) =207391a(19) =531243a(20) =946025a(21) =2423293a(22) =4315343a(23) =11053979a(24) =19684665a(25) =50423309a(26) =89792639a(27) =230008587a(28) =409593865a(29) =1049196317