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 A353584 #8 May 08 2022 04:55:06
%S A353584 1,1,3,3,15,15,315,105,567,405,155925,467775,1216215,34749,638512875,
%T A353584 638512875,2170943775,32564156625,1856156927625,3093594879375,
%U A353584 38979295480125,5568470782875,49308808782358125,2900518163668125,284473896821296875,1232720219558953125
%N A353584 Denominators of coefficients c(n) in product expansion of 1 + tan x = Product_{k>=1} 1 + c(k)*x^k.
%C A353584 See the sequence of numerators, A353583, for references and more.
%e A353584 1 + tan x = (1 + x)(1 + 1/3*x^3)(1 - 1/3*x^4/3)(1 + 7/15*x^5)(1 - 7/15*x^5)(...),
%e A353584 and this sequence lists the denominators of (1, 0, 1/3, -1/3, 7/15, -7/15, ...).
%o A353584 (PARI) t=1+tan(x+O(x)^29); vector(#t-1,n,c=polcoef(t,n);t/=1+c*x^n;denominator(c))
%Y A353584 Cf. A353583 (numerators)
%Y A353584 Cf. A170918 / A170919 for a variant.
%K A353584 nonn,frac
%O A353584 1,3
%A A353584 _M. F. Hasler_, May 07 2022