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 A380950 #15 Feb 14 2025 08:14:32
%S A380950 1,1,2,3,16,45,128,175,2048,11025,32768,43659,262144,693693,2097152,
%T A380950 2760615,67108864,703956825,2147483648,2807136475,17179869184,
%U A380950 44801898141,137438953472,178837328943,2199023255552,11425718238025,35184372088832,45635265151875,281474976710656
%N A380950 a(n) = denominator(r(n)) where r(n) = (n/2)*(Pi/2)^cos(Pi*(n-1))*((n/2-1/2)!/(n/2)!)^2.
%H A380950 Paolo Xausa, <a href="/A380950/b380950.txt">Table of n, a(n) for n = 0..1000</a>
%F A380950 See the formulas in A380949.
%p A380950 r := n -> (n/2)*(Pi/2)^cos(Pi*(n-1))*((n/2-1/2)!/(n/2)!)^2:
%p A380950 a := n -> denom(simplify(r(n))): seq(a(n), n = 0..28);
%p A380950 # Alternative:
%p A380950 r := n -> ifelse(n <= 1, n, (n - 1)/(n*r(n - 1))):
%t A380950 Join[{1}, Denominator[FoldList[(#2 - 1)/(#2*#) &, Range[30]]]] (* _Paolo Xausa_, Feb 14 2025 *)
%Y A380950 Cf. A380949 (numerator).
%K A380950 nonn,frac
%O A380950 0,3
%A A380950 _Peter Luschny_, Feb 11 2025