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 A081786 #19 Apr 24 2025 01:31:10
%S A081786 1,21,1591,5623795,60586207387643,11771746654268128293298294264,
%T A081786 223879928814222731378358322195036233470100990978181612407,
%U A081786 60370531495558553873551440308434816125184142701829318337696802178075590153432959525193229753905998692773283506988
%N A081786 Continued cotangent for log(3).
%F A081786 log(3) = cot(Sum_{n>=0} (-1)^n*acot(a(n))).
%F A081786 Let b(0) = log(3), b(n) = (b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1))) then a(n) = floor(b(n)).
%o A081786 (PARI) \p900
%o A081786 bn=vector(100);
%o A081786 bn[1]=log(3);
%o A081786 b(n)=if(n<0,0,bn[n]);
%o A081786 for(n=2,10,bn[n]=(b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1))));
%o A081786 a(n)=floor(b(n+1));
%Y A081786 Cf. A002666, A002667.
%K A081786 nonn
%O A081786 0,2
%A A081786 _Benoit Cloitre_, Apr 10 2003