a(n)=least k such that base 4 representation of n begins at s(k), where s=A030386.

Terms

a(0) =1a(1) =2a(2) =3a(3) =11a(4) =5a(5) =1a(6) =9a(7) =19a(8) =8a(9) =15a(10) =2a(11) =3a(12) =10a(13) =18a(14) =25a(15) =75a(16) =31a(17) =11a(18) =63a(19) =30a(20) =5a(21) =6a(22) =47a(23) =33a(24) =7a(25) =14a(26) =1a(27) =36a(28) =9a(29) =22