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 A079858 #29 Mar 16 2020 18:26:06
%S A079858 1,2,12,88,912,11552,176832,3150208,64188672,1470996992,37459479552,
%T A079858 1049279715328,32063706796032,1061443378552832,37841217707753472,
%U A079858 1445427909919080448,58892032991566036992,2549444593020567683072
%N A079858 E.g.f. 1/(cos(2*x) - sin(2*x)).
%H A079858 G. C. Greubel, <a href="/A079858/b079858.txt">Table of n, a(n) for n = 0..385</a>
%F A079858 E.g.f.: 1/(cos(2*x) - sin(2*x)).
%F A079858 a(n) = 2^n * A001586(n).
%F A079858 a(n) = | 2*8^n*lerchphi(-1,-n,1/4) |. - _Peter Luschny_, Apr 27 2013
%F A079858 G.f.: 1/Q(0), where Q(k) = 1 - 2*x*(2*k+1) - 8*x^2*(k+1)^2/Q(k+1) ; (continued fraction). - _Sergei N. Gladkovskii_, Sep 27 2013
%F A079858 a(n) ~ 4 * n^(n+1/2) * (8/Pi)^n / (sqrt(Pi)*exp(n)). - _Vaclav Kotesovec_, Oct 07 2013
%F A079858 E.g.f.: 1/(1-2*x)*(1 + 2*x^2/((1-2*x)*W(0) - x )), where W(k) = x + (k+1)/( 1 - 2*x/( 2*k+3 - x*(2*k+3)/W(k+1) )); (continued fraction ). - _Sergei N. Gladkovskii_, Dec 27 2013
%t A079858 CoefficientList[Series[1/(Cos[2*x]-Sin[2*x]), {x, 0, 20}], x]* Range[0, 20]! (* _Vaclav Kotesovec_, Oct 07 2013 *)
%o A079858 (PARI) a(n)=if(n<0,0,n!*polcoeff(1/(cos(2*x+x*O(x^n))-sin(2*x+x*O(x^n))),n))
%o A079858 (Sage)
%o A079858 from mpmath import mp, lerchphi
%o A079858 mp.dps = 32; mp.pretty = True
%o A079858 def A079858(n): return abs(2*8^n*lerchphi(-1,-n,1/4))
%o A079858 [int(A079858(n)) for n in (0..17)] # _Peter Luschny_, Apr 27 2013
%o A079858 (PARI) x='x+O('x^66); v=Vec(serlaplace( 1/(cos(2*x)-sin(2*x)) ) ) \\ _Joerg Arndt_, Apr 27 2013
%Y A079858 Cf. A001586.
%Y A079858 (-1)^(n*(n-1)/2)*a(n) gives the alternating row sums of A225118. - _Wolfdieter Lang_, Jul 12 2017
%K A079858 nonn,easy
%O A079858 0,2
%A A079858 _Michael Somos_, Jan 20 2003