a(n) = least k such that s(k) = n, where s = A026346.

Terms

a(0) =1a(1) =3a(2) =4a(3) =5a(4) =7a(5) =8a(6) =10a(7) =12a(8) =13a(9) =14a(10) =16a(11) =17a(12) =19a(13) =20a(14) =21a(15) =23a(16) =24a(17) =25a(18) =27a(19) =29a(20) =30a(21) =32a(22) =33a(23) =34a(24) =36a(25) =38a(26) =39a(27) =40a(28) =42a(29) =43