a(n)=least k such that the base 7 representation of n begins at s(k), where s=A031016.

Terms

a(0) =5a(1) =4a(2) =3a(3) =2a(4) =1a(5) =8a(6) =5a(7) =73a(8) =60a(9) =46a(10) =32a(11) =18a(12) =63a(13) =61a(14) =4a(15) =57a(16) =44a(17) =30a(18) =16a(19) =49a(20) =47a(21) =45a(22) =3a(23) =41a(24) =28a(25) =14a(26) =35a(27) =33a(28) =31a(29) =29