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 A051711 #35 Jul 02 2025 16:01:58
%S A051711 1,2,16,192,3072,61440,1474560,41287680,1321205760,47563407360,
%T A051711 1902536294400,83711596953600,4018156653772800,208944145996185600,
%U A051711 11700872175786393600,702052330547183616000,44931349155019751424000
%N A051711 a(0) = 1; for n > 0, a(n) = n!*4^n/2.
%C A051711 For n <= 16, denominators in expansion of W(exp(x)) about x=1, where W is the Lambert function.
%H A051711 G. C. Greubel, <a href="/A051711/b051711.txt">Table of n, a(n) for n = 0..365</a>
%H A051711 J. M. Borwein and R. M. Corless, <a href="https://wayback.cecm.sfu.ca/projects/IntegerRelations/MAA/emerging98.html">Emerging tools for experimental mathematics</a>.
%H A051711 J. M. Borwein and R. M. Corless, <a href="http://www.jstor.org/stable/2589743">Emerging tools for experimental mathematics</a>, Amer. Math. Monthly, 106 (No. 10, 1999), 889-909.
%H A051711 INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=647">Encyclopedia of Combinatorial Structures 647</a>
%F A051711 E.g.f.: (1-2*x)/(1-4*x).
%F A051711 a(n) = 4*n * a(n-1), n > 0.
%e A051711 W(exp(x)) = 1 + (x-1)/2 + (x-1)^2/16 - (x-1)^3/192 - ... .
%t A051711 Join[{1},Table[(n! 4^n)/2,{n,20}]] (* _Harvey P. Dale_, Oct 05 2012 *)
%o A051711 (PARI) a(n)=if(n<1,!n,4^n/2*n!)
%o A051711 (Magma) [1] cat [2^(2*n-1)*Factorial(n): n in [1..30]]; // _G. C. Greubel_, Mar 06 2018
%Y A051711 Cf. A001662.
%K A051711 nonn,easy,nice,frac
%O A051711 0,2
%A A051711 _N. J. A. Sloane_
%E A051711 More terms from _James Sellers_, Dec 07 1999
%E A051711 Edited by _Michael Somos_, Aug 21 2002