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 A086117 #17 Apr 08 2025 22:06:27
%S A086117 2,2,4,4,16,16,32,32,256,256,512,512,2048,2048,4096,4096,65536,65536,
%T A086117 131072,131072,524288,524288,1048576,1048576,8388608,8388608,16777216,
%U A086117 16777216,67108864,67108864,134217728,134217728,4294967296,4294967296
%N A086117 Denominator of mean deviation of a symmetrical binomial distribution on n elements.
%C A086117 Also denominator of x(n)=Sum(x(k)*x(n-k-1):0<=k<n), x(0)=1/2: x(n)=A098597(n)/a(n+2). - _Reinhard Zumkeller_, Feb 06 2008
%H A086117 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/BinomialDistribution.html">Binomial Distribution</a>
%H A086117 <a href="/index/Di#divseq">Index to divisibility sequences</a>
%F A086117 a(1)=2, a(n) = a(n-1)*A006519(n). - _Jon Perry_, Mar 31 2004
%F A086117 a(n) = 2^A113474(n-1). - _Alan Michael Gómez Calderón_, Apr 03 2025
%t A086117 Denominator[Table[If[OddQ[n], n!!/2/(n-1)!!, (n-1)!!/2/(n-2)!! ], {n, 50}]]
%Y A086117 Cf. A086116, A113474.
%Y A086117 Twice A101926.
%K A086117 nonn,frac
%O A086117 1,1
%A A086117 _Eric W. Weisstein_, Jul 10 2003