Base -2 representation for n regarded as base 2, then evaluated.

Terms

a(0) =0a(1) =1a(2) =6a(3) =7a(4) =4a(5) =5a(6) =26a(7) =27a(8) =24a(9) =25a(10) =30a(11) =31a(12) =28a(13) =29a(14) =18a(15) =19a(16) =16a(17) =17a(18) =22a(19) =23a(20) =20a(21) =21a(22) =106a(23) =107a(24) =104a(25) =105a(26) =110a(27) =111a(28) =108a(29) =109