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

Terms

a(0) =1a(1) =3a(2) =5a(3) =11a(4) =25a(5) =55a(6) =121a(7) =267a(8) =589a(9) =1299a(10) =2865a(11) =6319a(12) =13937a(13) =30739a(14) =67797a(15) =149531a(16) =329801a(17) =727399a(18) =1604329a(19) =3538459a(20) =7804317a(21) =17212963a(22) =37964385a(23) =83733087a(24) =184679137a(25) =407322659a(26) =898378405a(27) =1981435947a(28) =4370194553a(29) =9638767511