a(n)=least k such that base 5 representation of n begins at s(k), where s=A031253.

Terms

a(0) =1a(1) =6a(2) =2a(3) =8a(4) =3a(5) =32a(6) =5a(7) =1a(8) =7a(9) =39a(10) =6a(11) =42a(12) =11a(13) =45a(14) =13a(15) =2a(16) =15a(17) =12a(18) =17a(19) =54a(20) =19a(21) =8a(22) =21a(23) =18a(24) =23a(25) =3a(26) =26a(27) =205a(28) =29a(29) =188