a(n) = greatest k such that s(k) = n, where s = A026276.

Terms

a(0) =4a(1) =6a(2) =8a(3) =11a(4) =14a(5) =17a(6) =19a(7) =22a(8) =24a(9) =27a(10) =29a(11) =32a(12) =35a(13) =37a(14) =40a(15) =43a(16) =45a(17) =48a(18) =51a(19) =53a(20) =56a(21) =58a(22) =61a(23) =64a(24) =66a(25) =69a(26) =71a(27) =74a(28) =77a(29) =79