Lucas 9-step numbers.

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =31a(5) =63a(6) =127a(7) =255a(8) =511a(9) =1013a(10) =2025a(11) =4047a(12) =8087a(13) =16159a(14) =32287a(15) =64511a(16) =128895a(17) =257535a(18) =514559a(19) =1028105a(20) =2054185a(21) =4104323a(22) =8200559a(23) =16384959a(24) =32737631a(25) =65410751a(26) =130692607a(27) =261127679a(28) =521740799a(29) =1042453493