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 A003414 #24 Oct 21 2023 19:51:09
%S A003414 -1,0,-1,0,-1,0,-1,0,-2,13,-141,1803,-27414,487468,-10026348,
%T A003414 236192433,-6317862398,190439655626,-6425425249653,241207241774250,
%U A003414 -10020155328258127,458387180159766538,-22989944171828251746,1259023596072554784854,-75008667460769643668558
%N A003414 a(n) = floor( Bernoulli(2*n)/(-4*n) ).
%D A003414 F. Hirzebruch et al., Manifolds and Modular Forms, Vieweg, 2nd ed. 1994, p. 130.
%D A003414 D. C. Ravenel, Complex cobordism theory for number theorists, Lecture Notes in Mathematics, 1326, Springer-Verlag, Berlin-New York, 1988, pp. 123-133.
%H A003414 T. D. Noe, <a href="/A003414/b003414.txt">Table of n, a(n) for n = 1..100</a>
%H A003414 <a href="/index/Be#Bernoulli">Index entries for sequences related to Bernoulli numbers</a>.
%e A003414 a(10) = 13 because the 20th (2 * 10) Bernoulli number is -174611/330, and that divided by (-4) * 10 is approximately 13.2281.
%t A003414 Table[Floor[BernoulliB[2n]/(-4n)], {n, 24}] (* _Alonso del Arte_, Jul 11 2012 *)
%Y A003414 Cf. A000367/A002445.
%K A003414 sign
%O A003414 1,9
%A A003414 _N. J. A. Sloane_