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 A006268 A continued cotangent. (Formerly M3141) 12
 3, 36, 46764, 102266868132036, 1069559300034650646049671039050649693658764 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Jeffrey Shallit, Predictable regular continued cotangent expansions, J. Res. Nat. Bur. Standards Sect. B 80B (1976), no. 2, 285-290. FORMULA From Artur Jasinski, Oct 03 2008: (Start) a(n+1) = a(n)^3 + 3*a(n) and a(0)=3. a(n) = round((3/2 + sqrt(13)/2)^(3^(n - 1))). (End) MATHEMATICA a = {}; k = 3; Do[AppendTo[a, k]; k = k^3 + 3 k, {n, 1, 6}]; a (* Artur Jasinski, Oct 03 2008 *) Table[Round[N[(3/2 + Sqrt[13]/2)^(3^(n - 1)), 1000]], {n, 1, 8}] (* Artur Jasinski, Oct 03 2008 *) PROG (PARI) a(n) = if (n==0, 3, a(n-1)^3 + 3*a(n-1)); \\ Michel Marcus, Aug 28 2020 CROSSREFS Sequence in context: A262825 A088322 A080807 * A264842 A210508 A073236 Adjacent sequences:  A006265 A006266 A006267 * A006269 A006270 A006271 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 26 16:43 EDT 2020. Contains 337374 sequences. (Running on oeis4.)