Jacobsthal-Lucas numbers.

Terms

a(0) =2a(1) =1a(2) =5a(3) =7a(4) =17a(5) =31a(6) =65a(7) =127a(8) =257a(9) =511a(10) =1025a(11) =2047a(12) =4097a(13) =8191a(14) =16385a(15) =32767a(16) =65537a(17) =131071a(18) =262145a(19) =524287a(20) =1048577a(21) =2097151a(22) =4194305a(23) =8388607a(24) =16777217a(25) =33554431a(26) =67108865a(27) =134217727a(28) =268435457a(29) =536870911