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 A089266 #13 Oct 11 2013 16:49:15
%S A089266 2,3,4,4,6,7,6,9,10,8,12,11,10,15,16,12,14,19,14,21,22,14,24,22,18,27,
%T A089266 22,20,30,31,20,26,34,24,36,37,22,32,40,28,42,34,30,45,38,32,38,49,32,
%U A089266 51,52,28,54,55,38,57,46,38,50,56,42,51,64,44,66,56
%N A089266 Rational knots of determinant 2n+1, counting chiral pairs twice.
%H A089266 Vincenzo Librandi, <a href="/A089266/b089266.txt">Table of n, a(n) for n = 1..1000</a>
%H A089266 A. Stoimenow, <a href="http://arxiv.org/abs/math.GT/0003172">Square numbers, spanning trees and invariants of rational knots</a> (2000)
%F A089266 a(n) = 1/2 * (A037225(n) + A034444(2*n+1)).
%t A089266 a[n_] := (EulerPhi[2*n+1] + 2^PrimeNu[2*n+1])/2; Table[a[n], {n, 1, 66}] (* _Jean-François Alcover_, Oct 11 2013, after Pari *)
%o A089266 (PARI) a(n)=(eulerphi(2*n+1)+2^omega(2*n+1))/2
%Y A089266 Cf. A078477, A078478, A018240, A051449, A051766.
%K A089266 nonn,easy,nice
%O A089266 1,1
%A A089266 _Ralf Stephan_, Oct 30 2003