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 A353586 #11 May 08 2022 04:53:46
%S A353586 1,2,1,53,91,811,73267,35540711,49830764,34241488,35249288479,
%T A353586 19259769465311,732125336837021,619038578481164306,
%U A353586 30015706187367326893,16177789439326291541,46789354983174555461,498213391899375541476686,248130101882943187003954597,2572596069535443792125179632949
%N A353586 Numerators of coefficients c(n) in product expansion of (tan x)/x = Product_{k>=1} 1 + c(k)*x^(2k).
%C A353586 The coefficients of odd powers are zero since (tan x)/x is an even function.
%C A353586 See A353587 for the denominators, and A353583 (similar for 1 + tan x) for references and more.
%e A353586 (tan x)/x = (1 + 1/3*x^2)(1 + 2/15*x^4)(1 + 1/105*x^6)(1 + 53/2835*x^8)...
%e A353586 and this sequence lists the numerators of (1/3, 2/15, 1/105, 53/2835, ...).
%o A353586 (PARI) t=tan(x+O(x)^58)/x; vector(#t\2,n,c=polcoef(t,n*2);t/=1+c*x^(n*2);numerator(c))
%Y A353586 Cf. A353587 (denominators); A353583 / A353584 (product expansion of 1 + tan x).
%Y A353586 Cf. A170918 / A170919 for a variant.
%K A353586 nonn,frac
%O A353586 1,2
%A A353586 _M. F. Hasler_, May 07 2022