Nimsum n + 21.

Terms

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