Interleave 2^n + 2 and 2^n + 1.

Terms

a(0) =4a(1) =3a(2) =6a(3) =5a(4) =10a(5) =9a(6) =18a(7) =17a(8) =34a(9) =33a(10) =66a(11) =65a(12) =130a(13) =129a(14) =258a(15) =257a(16) =514a(17) =513a(18) =1026a(19) =1025a(20) =2050a(21) =2049a(22) =4098a(23) =4097a(24) =8194a(25) =8193a(26) =16386a(27) =16385a(28) =32770a(29) =32769