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

Terms

a(0) =1a(1) =1a(2) =4a(3) =11a(4) =33a(5) =98a(6) =293a(7) =877a(8) =2628a(9) =7879a(10) =23629a(11) =70874a(12) =212601a(13) =637769a(14) =1913252a(15) =5739667a(16) =17218857a(17) =51656338a(18) =154968637a(19) =464905301a(20) =1394714916a(21) =4184143151a(22) =12552426869a(23) =37657276426a(24) =112971822513a(25) =338915456593