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 A081790 #18 Apr 23 2025 19:12:46
%S A081790 1,4,32,1158,1815746,15716561494212,1184500978807872650350593387,
%T A081790 5321879016477546178356935033926215638755808624425727229,
%U A081790 28586857373644233013728565794450100157386617152409721820238727067747604580786570816033645416762395120483912199
%N A081790 Continued cotangent for tan(1).
%D A081790 D. H. Lehmer, A cotangent analogue of continued fractions, Duke Math. J., 4 (1935), 323-340.
%F A081790 tan(1) = cot(Sum_{n>=0} (-1)^n*acot(a(n))).
%F A081790 Let b(0) = tan(1), b(n) = (b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1))) then a(n) = floor(b(n)).
%o A081790 (PARI) bn=vector(100);
%o A081790 b(n)=if(n<0,0,bn[n]);
%o A081790 bn[1]=tan(1);
%o A081790 for(n=2,10,bn[n]=(b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1))));
%o A081790 a(n)=floor(b(n+1));
%Y A081790 Cf. A002666, A002667, A002668.
%K A081790 nonn
%O A081790 0,2
%A A081790 _Benoit Cloitre_, Apr 10 2003