a(n)=least k such that base 10 representation of n begins at s(k), where s=A031298.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =29a(10) =11a(11) =1a(12) =15a(13) =17a(14) =19a(15) =21a(16) =23a(17) =25a(18) =27a(19) =49a(20) =14a(21) =33a(22) =2a(23) =37a(24) =39a(25) =41a(26) =43a(27) =45a(28) =47a(29) =69