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 A032107 #10 May 11 2025 13:07:51
%S A032107 2,4,24,192,1920,23040,322560,5160960,92897280,1857945600,40874803200,
%T A032107 980995276800,25505877196800,714164561510400,21424936845312000,
%U A032107 685597979049984000,23310331287699456000
%N A032107 Number of reversible strings with n labeled beads of 2 colors.
%H A032107 C. G. Bower, <a href="/transforms2.html">Transforms (2)</a>
%F A032107 2^(n-1)*n! (n>1). E.g.f.: (1-2*x^2)/(1-2*x). Also "BIJ" (reversible, indistinct, labeled) transform of 2, 0, 0, 0...
%t A032107 Join[{2},Table[2^(n-1) n!,{n,2,20}]] (* _Harvey P. Dale_, May 11 2025 *)
%K A032107 nonn
%O A032107 1,1
%A A032107 _Christian G. Bower_
%E A032107 Essentially same as A002866.