Nimsum n + 20.

Terms

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