Decimal equivalent of Gray code for n.

Terms

a(0) =0a(1) =1a(2) =3a(3) =2a(4) =6a(5) =7a(6) =5a(7) =4a(8) =12a(9) =13a(10) =15a(11) =14a(12) =10a(13) =11a(14) =9a(15) =8a(16) =24a(17) =25a(18) =27a(19) =26a(20) =30a(21) =31a(22) =29a(23) =28a(24) =20a(25) =21a(26) =23a(27) =22a(28) =18a(29) =19