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 A309340 #11 Aug 08 2019 17:24:32 %S A309340 0,1,2,4,9,38,304,2433,38938,2492040,318981139,163318343502 %N A309340 a(n) is the least nonnegative number whose binary digits do not appear in order (not necessarily consecutively) in the concatenation of the binary representations of all previous terms. %C A309340 This sequence is a variant of A118248. %C A309340 a(13) > 4.5*10^12. - _Giovanni Resta_, Aug 08 2019 %Y A309340 See A308540 for the decimal variant. %Y A309340 Cf. A118248. %K A309340 nonn,base,hard,more %O A309340 1,3 %A A309340 _Rémy Sigrist_, Jul 24 2019 %E A309340 a(12) from _Giovanni Resta_, Aug 08 2019