Search: id:A081781
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%I A081781
%S A081781 2,23,2961,9798690,110528843365255,16850689692769666225948933906,
%T A081781 357017084742873887104901208145335336566095925224005385073,
%U A081781 1370463934077426882817816433186442892496272312967796657134064415099753673103182423835233031765649090845942473\
               59836
%N A081781 Continued cotangent for square root of 5.
%F A081781 sqrt(5)=cot(sum(n>=0, n, (-1)^n*acot(a(n))); let b(0)=sqrt(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 A081781 (PARI) ?bn=vector(100); b(n)=if(n<0,0,bn[n]); bn[1]=sqrt(5); ?for(n=2,
               10,bn[n]=(b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1)))) ?a(n)=floor(b(n+1))
%Y A081781 Cf. A002666, A002667.
%Y A081781 Sequence in context: A069151 A091763 A124513 this_sequence A088734 A087388 
               A117507
%Y A081781 Adjacent sequences: A081778 A081779 A081780 this_sequence A081782 A081783 
               A081784
%K A081781 nonn
%O A081781 0,1
%A A081781 Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 10 2003

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