a(2n) = 2*2^n - 1, a(2n+1) = 3*2^n - 1.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =7a(5) =11a(6) =15a(7) =23a(8) =31a(9) =47a(10) =63a(11) =95a(12) =127a(13) =191a(14) =255a(15) =383a(16) =511a(17) =767a(18) =1023a(19) =1535a(20) =2047a(21) =3071a(22) =4095a(23) =6143a(24) =8191a(25) =12287a(26) =16383a(27) =24575a(28) =32767a(29) =49151