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 A000488 M5024 N2167 #31 May 07 2018 22:21:26
%S A000488 16,361,3362,16384,55744,152166,355688,739328,1415232,2529614,4261454,
%T A000488 6885376,10708160,16054580,23494584,33554432,46698624,64037790,
%U A000488 86342918,114163712,149518720,193356526,246232840,311635968,390600000
%N A000488 Generalized tangent numbers d_(n,3).
%D A000488 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A000488 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A000488 Lars Blomberg, <a href="/A000488/b000488.txt">Table of n, a(n) for n = 1..1000</a>
%H A000488 D. Shanks, <a href="http://dx.doi.org/10.1090/S0025-5718-1967-0223295-5">Generalized Euler and class numbers</a>. Math. Comp. 21 (1967) 689-694.
%H A000488 D. Shanks, <a href="http://dx.doi.org/10.1090/S0025-5718-1968-0227093-9">Corrigenda to: "Generalized Euler and class numbers"</a>, Math. Comp. 22 (1968), 699
%t A000488 amax = 25; km0 = 10; L[a_, s_, km_] := Sum[JacobiSymbol[-a, 2 k + 1]/(2 k + 1)^s, {k, 0, km}]; d[1, n_, km_] := 2 (2 n - 1)! L[-1, 2 n, km] (2/Pi)^(2 n) // Round; d[a_ /; a > 1, n_, km_] := (2 n - 1)! L[-a, 2 n, km] (2 a/Pi )^(2 n)/Sqrt[a] // Round; dd[km_] := dd[km] = Table[d[a, 3, km], {a, 1, amax}]; dd[km0]; dd[km = 2 km0]; While[dd[km] != dd[km/2, km = 2 km]]; A000488 = dd[km] (* _Jean-François Alcover_, Feb 08 2016 *)
%Y A000488 Cf. A000061, A000176, A000518.
%K A000488 nonn
%O A000488 1,1
%A A000488 _N. J. A. Sloane_
%E A000488 More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Jun 03 2000