a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3).

Terms

a(0) =1a(1) =3a(2) =5a(3) =9a(4) =13a(5) =21a(6) =29a(7) =45a(8) =61a(9) =93a(10) =125a(11) =189a(12) =253a(13) =381a(14) =509a(15) =765a(16) =1021a(17) =1533a(18) =2045a(19) =3069a(20) =4093a(21) =6141a(22) =8189a(23) =12285a(24) =16381a(25) =24573a(26) =32765a(27) =49149a(28) =65533a(29) =98301