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 A051426 #29 Oct 27 2023 22:00:44
%S A051426 2,4,12,24,120,120,840,1680,5040,5040,55440,55440,720720,720720,
%T A051426 720720,1441440,24504480,24504480,465585120,465585120,465585120,
%U A051426 465585120,10708457760,10708457760,53542288800,53542288800,160626866400,160626866400,4658179125600
%N A051426 Least common multiple of {2, 4, 6, ..., 2n}.
%C A051426 Gcd(A025547(n), a(n)) = A025547(floor((n+1)/2)). - _Reinhard Zumkeller_, Apr 25 2011
%D A051426 A. Murthy, Some new Smarandache sequences, functions and partitions, Smarandache Notions Journal Vol. 11 N. 1-2-3 Spring 2000 (but beware errors).
%H A051426 T. D. Noe, <a href="/A051426/b051426.txt">Table of n, a(n) for n = 1..500</a>
%H A051426 <a href="/index/Lc#lcm">Index entries for sequences related to lcm's</a>
%F A051426 a(n) = a(n-1)*lcm(a(n-1),2n) = a(n-1)* A014963(n). - _Zak Seidov_, Aug 01 2009
%e A051426 a(3) = lcm{2,4,6} = 12;
%e A051426 a(7) = lcm{2,4,6,8,10,12,14} = 840.
%t A051426 SZ={2};n=2;L=2;Do[L=LCM[L,2n];AppendTo[SZ,L];n++,{99}];SZ (* _Zak Seidov_, Aug 01 2009 *)
%t A051426 Table[LCM@@Range[2,2n,2],{n,30}] (* _Harvey P. Dale_, Oct 09 2011 *)
%o A051426 (Haskell)
%o A051426 a051426 n = foldl lcm 1 [2,4..2*n] -- _Reinhard Zumkeller_, Apr 25 2011
%o A051426 (PARI) a(n)=2*lcm([1..n]) \\ _Charles R Greathouse IV_, Oct 28 2016
%Y A051426 Cf. A003418, A025547.
%K A051426 easy,nice,nonn
%O A051426 1,1
%A A051426 _Asher Auel_
%E A051426 a(6), a(7) and a(8) corrected by _T. D. Noe_, Feb 08 2008
%E A051426 Corrected the example, which did not reflect the sequence values provided. - Michael Davies (mykdavies+oeis(AT)gmail.com), Oct 10 2008
%E A051426 Edited by _N. J. A. Sloane_, Jul 31 2009 at the suggestion of _R. J. Mathar_