This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A262279 #27 Sep 21 2023 11:10:13 %S A262279 0,1,2,6,75 %N A262279 Smallest m such that A261923(m) = n. %C A262279 A261923(m) != 5 for m <= 10^5. %C A262279 The same for m <= 5*10^8. - _Michel Marcus_, Sep 20 2023 %C A262279 From _Michael S. Branicky_, Sep 21 2023: (Start) %C A262279 a(5) <= 10718873460460617403023221866359404479. %C A262279 a(n) exists for all n. Proof. Let b(i) be the binary representation of i. Let L be its length, and w = 0^L be a string of L 0's. Then a(n+1) <= u = b(1)wb(2)w...wb(a(n)-1)_2 since u's binary representation contains that of each number less than a(n) but not that of a(n). So, A261923(u) = 1 + A261923(a(n)). (End) %o A262279 (Haskell) %o A262279 import Data.List (elemIndex); import Data.Maybe (fromJust) %o A262279 a262279 = fromJust . (`elemIndex` a261923_list) %o A262279 (PARI) a(n) = my(k=0); while (A261923(k) != n, k++); k; \\ _Michel Marcus_, Sep 20 2023 %Y A262279 Cf. A056744, A261923. %K A262279 nonn,more %O A262279 0,3 %A A262279 _Reinhard Zumkeller_, Sep 17 2015