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 A000723 M3180 N1289 #42 Jun 01 2025 00:53:23
%S A000723 1,3,840,54486432000,68523655451482690147713024000000,
%T A000723 2753622660283944533494648206058191857701074569760095316814277221684346880000000000000
%N A000723 Invertible Boolean functions of n variables.
%C A000723 Equivalence classes of invertible maps from {0,1}^n to {0,1}^n, under action of (C_2)^n on domain and permutation of variables on range. - _Sean A. Irvine_, Mar 15 2011
%C A000723 Also the number of distinct adjacency matrices of the n-hypercube graph Q_n. - _Eric W. Weisstein_, Mar 31 2017
%D A000723 M. A. Harrison, The number of classes of invertible Boolean functions, J. ACM 10 (1963), 25-28.
%D A000723 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A000723 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A000723 Vincenzo Librandi, <a href="/A000723/b000723.txt">Table of n, a(n) for n = 1..8</a>
%H A000723 M. A. Harrison, <a href="/A000653/a000653.pdf">The number of classes of invertible Boolean functions</a>, J. ACM 10 (1963), 25-28. [Annotated scan of page 27 only]
%H A000723 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AdjacencyMatrix.html">Adjacency Matrix</a>
%H A000723 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HypercubeGraph.html">Hypercube Graph</a>
%H A000723 <a href="/index/Bo#Boolean">Index entries for sequences related to Boolean functions</a>
%F A000723 a(n) = (2^n-1)!/n!. - _Sean A. Irvine_, Mar 15 2011
%t A000723 f[n_] := (2^n - 1)!/n!; Array[f, 6] (* _Robert G. Wilson v_, Mar 14 2011 *)
%t A000723 Table[Gamma[2^n]/n!, {n, 6}] (* _Eric W. Weisstein_, Mar 31 2017 *)
%o A000723 (Magma) [Factorial(2^n - 1)/Factorial(n): n in [1..10]]; // _Vincenzo Librandi_, Mar 28 2012
%K A000723 nonn
%O A000723 1,2
%A A000723 _N. J. A. Sloane_
%E A000723 More terms from _Sean A. Irvine_, Mar 14 2011