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A006266
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A continued cotangent.
(Formerly M2073)
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14
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OFFSET
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1,1
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COMMENTS
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The next (7th) term is 280 digits long. - M. F. Hasler, Oct 06 2014
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Table of n, a(n) for n=1..6.
J. Shallit, Predictable regular continued cotangent expansions, J. Res. Nat. Bur. Standards Sect. B 80B (1976), no. 2, 285-290.
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FORMULA
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a(n+1) = a(n)^3 + 3*a(n) with a(1)=2. a(n+1)=round((1+sqrt(2))^(3^n)). - Artur Jasinski, Sep 24 2008, Corrected by M. F. Hasler, Oct 06 2014
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MATHEMATICA
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a = {}; k = 2; Do[AppendTo[a, k]; k = k^3 + 3 k, {n, 1, 10}]; a (* or: *)
Table[Round[(1+Sqrt[2])^(3^n)], {n, 0, 10}] (* Artur Jasinski, Sep 24 2008 *)
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PROG
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(PARI) a(n, s=2)=for(i=2, n, s*=(s^2+3)); s \\ M. F. Hasler, Oct 06 2014
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CROSSREFS
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Cf. A006267. - Artur Jasinski, Sep 24 2008
Sequence in context: A277288 A296412 A296410 * A284378 A106484 A228342
Adjacent sequences: A006263 A006264 A006265 * A006267 A006268 A006269
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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Edited by M. F. Hasler, Oct 06 2014
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STATUS
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approved
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