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 A162890 #11 Jan 03 2024 22:04:52 %S A162890 1,2,3,15,24,25 %N A162890 The set of exotic numbers A064818 extended by allowing the double factorials A006882 into the set of operations. %e A162890 Using double factorials (!!) augments A064818 for example by 3 = 3!! and by 15 = (5!!)*1 = (5!!)/1 = (5!!)^1. %Y A162890 Cf. A006882, A064818. %K A162890 more,nonn %O A162890 1,2 %A A162890 _Paolo P. Lava_ & _Giorgio Balzarotti_, Jul 16 2009 %E A162890 Definition rephrased by _R. J. Mathar_, Aug 27 2009