a(n)=least k such that base 7 representation of n begins at s(k), where s=A030998.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =9a(8) =1a(9) =13a(10) =15a(11) =17a(12) =19a(13) =21a(14) =12a(15) =25a(16) =2a(17) =29a(18) =31a(19) =33a(20) =35a(21) =14a(22) =28a(23) =41a(24) =3a(25) =45a(26) =47a(27) =49a(28) =16a(29) =30