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 A013528 #14 Nov 12 2016 18:08:33
%S A013528 1,-1,-1,1,19,25031,18421,-622177,-283401163,-24826632949,-2243454779,
%T A013528 4882905709651,43798187793808543,-46704901267812186793,
%U A013528 -5325187532598955153807
%N A013528 Numerator of [x^(2n)] of the Taylor series sech(cosec(x)-cot(x)) = 1 -x^2/8 -x^4/128 +x^6/15360 +19*x^8/294912 +25031*x^10/3715891200+... .
%C A013528 The e.g.f. related to x/2, sech(cosec(x)-cot(x)) = 1 -1*x^2/(2^2*2!) -3*x^4*(2^4*4!) +3*x^6/(2^6*6!) +665*x^8/(2^8*8!) +.. is (up to signs) apparently provided by A009011.
%H A013528 G. C. Greubel, <a href="/A013528/b013528.txt">Table of n, a(n) for n = 0..200</a>
%t A013528 Numerator[Take[CoefficientList[Series[Sech[Csc[x] - Cot[x]], {x,0,50}], x], {1, -1, 2}]] (* _G. C. Greubel_, Nov 12 2016 *)
%K A013528 sign,frac
%O A013528 0,5
%A A013528 Patrick Demichel (patrick.demichel(AT)hp.com)
%E A013528 Name edited by _R. J. Mathar_, Dec 20 2011