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 A057868 #29 Dec 03 2022 16:31:17
%S A057868 48,5760,362880,19353600,958003200,31384184832000,2092278988800,
%T A057868 341459930972160000,183927391818153984000,32114306507931648000000,
%U A057868 620448401733239439360000,81303558563123696133734400000,9678995067038535254016000000,2122022878497528469090467840000000
%N A057868 Denominator of "modified Bernoulli number" b(2n) = Bernoulli(2*n)/(4*n*(2*n)!).
%C A057868 Note that Weisstein gives the formula b(n) = B(n)/(2*n*n!), and a(n) is the denominator of b(2*n). Numerators seem to be A141590 (not A001067 or A046968 or A255505). - _Andrey Zabolotskiy_, Dec 03 2022
%H A057868 D. Bar-Natan, T. T. Q. Le and D. P. Thurston, <a href="https://arxiv.org/abs/math/0204311">Two applications of elementary knot theory to Lie algebras and Vassiliev invariants</a>, Geometry and Topology 7-1 (2003) 1-31.
%H A057868 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ModifiedBernoulliNumber.html">Modified Bernoulli Numbers</a>.
%H A057868 <a href="/index/Be#Bernoulli">Index entries for sequences related to Bernoulli numbers</a>.
%e A057868 The sequence of modified Bernoulli numbers begins 1/48, -1/5760, 1/362880, -1/19353600, 1/958003200, -691/31384184832000, ...
%p A057868 seq(denom(bernoulli(2*n)/((4*n)*(2*n)!)), n = 1..14); # _Peter Luschny_, Dec 03 2022
%t A057868 a[n_] := Denominator[ BernoulliB[2n] / (8n^2*(2n-1)!)];
%t A057868 Table[a[n], {n, 1, 12}] (* _Jean-François Alcover_, Jun 07 2012 *)
%Y A057868 Numerators seem to be A141590.
%Y A057868 Cf. A001067.
%K A057868 nonn,frac
%O A057868 1,1
%A A057868 _Eric W. Weisstein_
%E A057868 Name edited by _Andrey Zabolotskiy_, Dec 03 2022