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 A353587 #5 May 08 2022 04:54:09
%S A353587 3,15,105,2835,66825,3648645,383107725,97692469875,1856156927625,
%T A353587 5568470782875,9056719980433125,33283445928091734375,
%U A353587 1298054391195577640625,3952575621190533915703125,367589532770719654160390625,112527407991036628824609375,3842566358093920359949921875
%N A353587 Denominators of coefficients c(n) in product expansion of (tan x)/x = Product_{k>=1} 1 + c(k)*x^(2k).
%C A353587 The coefficients of odd powers are zero since (tan x)/x is an even function.
%e A353587 (tan x)/x = (1 + 1/3*x^2)(1 + 2/15*x^4)(1 + 1/105*x^6)(1 + 53/2835*x^8)...
%e A353587 and this sequence lists the denominators of (1/3, 2/15, 1/105, 53/2835, ...).
%o A353587 (PARI) t=tan(x+O(x)^58)/x; vector(#t\2,n,c=polcoef(t,n*2);t/=1+c*x^(n*2);denominator(c))
%Y A353587 Cf. A353586 (numerators); A353583 / A353584 (product expansion of 1 + tan x).
%Y A353587 Cf. A170918 / A170919 for a variant.
%K A353587 nonn,frac
%O A353587 1,1
%A A353587 _M. F. Hasler_, May 07 2022