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 A004735 #19 Oct 26 2023 08:42:20
%S A004735 1,3,4,15,8,35,64,315,128,693,512,3003,1024,6435,16384,109395,32768,
%T A004735 230945,131072,969969,262144,2028117,2097152,16900975,4194304,
%U A004735 35102025,16777216,145422675,33554432
%N A004735 Denominator of average distance traveled by n-dimensional fly.
%C A004735 The average distance is actually d(n) = 2*n!!/(n+1)!! if n is odd, and d(n) = (1*Pi)*4*n!!/(n+1)!! if n is even. So a(n) = denominator(d(n)) if n is odd and a(n) = denominator(Pi*d(n)) if n is even. - _Michel Marcus_, May 24 2013
%D A004735 S. Janson, On the traveling fly problem, Graph Theory Notes of New York, Vol. XXXI, 17, 1996.
%H A004735 S. Janson, <a href="http://www2.math.uu.se/~svante/papers/sj114.pdf">On the traveling fly problem</a>.
%F A004735 a(2n) = A001803(n) (conjectured). - _Ralf Stephan_, Mar 10 2004
%o A004735 (PARI) a(n) = {if (n % 2, eo = 2, eo = 4); denominator(eo*prod(i=0, floor((n-1)/2), n-2*i)/prod(i=0, floor(n/2), n+1-2*i));} \\ _Michel Marcus_, May 24 2013
%Y A004735 Cf. A004734.
%K A004735 nonn,frac
%O A004735 1,2
%A A004735 _N. J. A. Sloane_