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Search: id:A081781
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| A081781 |
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Continued cotangent for square root of 5. |
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+0
1
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| 2, 23, 2961, 9798690, 110528843365255, 16850689692769666225948933906, 357017084742873887104901208145335336566095925224005385073, 13704639340774268828178164331864428924962723129677966571340644150997536731031824\ 2383523303176564909084594247359836
(list; graph; listen)
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OFFSET
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0,1
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FORMULA
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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))
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PROGRAM
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(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))
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CROSSREFS
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Cf. A002666, A002667.
Sequence in context: A069151 A091763 A124513 this_sequence A088734 A087388 A117507
Adjacent sequences: A081778 A081779 A081780 this_sequence A081782 A081783 A081784
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 10 2003
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