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 A013517 #24 Mar 18 2019 09:51:43
%S A013517 2,48,1280,129024,1769472,81749606400,4637432217600,3296144130048000,
%T A013517 46620662575398912000,750318428272302489600,5639235345120252395520000,
%U A013517 72287478143981475374039040000,7543041197632849604247552000000,1461479318123759876522171695104000000,4746884825265972078944013665697792000000
%N A013517 Denominator of [x^(2n+1)] in the Taylor expansion sin(cosec(x)-cot(x))= x/2 + x^3/48 - x^5/1280 - 55*x^7/129024 - 143*x^9/1769472 + ...
%C A013517 Numerators are apparently provided by A096664.
%F A013517 a(n) = A096671(n) * 2^(2*n+1). - _Sean A. Irvine_, Aug 07 2018
%e A013517 sin(cosec(x) - cot(x)) = x/(2^1*1!) + x^3/(2^3*3!) - 3*x^5/(2^5*5!) - 275*x^7/(2^7*7!) - 15015*x^9/(2^9*9!) - 968167*x^11/(2^11*11!) + ... (apparently covered by A003706).
%o A013517 (PARI) x = 'x + O('x^50); v = apply(x->denominator(x), Vec(sin(1/sin(x)-cotan(x)))); vector(#v\2, k, v[2*k-1]) \\ _Michel Marcus_, Sep 20 2018
%Y A013517 Cf. A096664, A096671.
%K A013517 nonn,frac
%O A013517 0,1
%A A013517 Patrick Demichel (patrick.demichel(AT)hp.com)
%E A013517 Corrected by _R. J. Mathar_, Dec 18 2011
%E A013517 More terms from _Michel Marcus_, Sep 20 2018