Least k such that base 4 representation of n begins at s(k), where s=A030373.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =6a(5) =1a(6) =10a(7) =12a(8) =9a(9) =16a(10) =2a(11) =20a(12) =3a(13) =11a(14) =19a(15) =28a(16) =4a(17) =34a(18) =37a(19) =33a(20) =6a(21) =7a(22) =49a(23) =52a(24) =8a(25) =15a(26) =1a(27) =64a(28) =50a(29) =10