a(n) = greatest k such that s(k) = n, where s = A026338.

Terms

a(0) =2a(1) =5a(2) =7a(3) =10a(4) =13a(5) =14a(6) =17a(7) =19a(8) =23a(9) =25a(10) =28a(11) =31a(12) =32a(13) =34a(14) =37a(15) =40a(16) =41a(17) =44a(18) =46a(19) =50a(20) =53a(21) =55a(22) =58a(23) =59a(24) =64a(25) =65a(26) =68a(27) =71a(28) =73a(29) =74