a(n+1) = 2^(2*n - 1) + (-1)^n * a(n), a(1) = 1.

Terms

a(0) =1a(1) =1a(2) =9a(3) =23a(4) =151a(5) =361a(6) =2409a(7) =5783a(8) =38551a(9) =92521a(10) =616809a(11) =1480343a(12) =9868951a(13) =23685481a(14) =157903209a(15) =378967703a(16) =2526451351a(17) =6063483241a(18) =40423221609a(19) =97015731863a(20) =646771545751