A216647 - OEIS

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A216647

a(n) := card{cos((2^(k-1))*Pi/n): k=1,2,...}.

2, 3, 2, 4, 3, 3, 4, 5, 4, 4, 6, 4, 7, 5, 5, 6, 5, 5, 10, 5, 7, 7, 12, 5, 11, 8, 10, 6, 15, 6, 6, 7, 6, 6, 13, 6, 19, 11, 13, 6, 11, 8, 8, 8, 13, 13, 24, 6, 22, 12, 9, 9, 27, 11, 21, 7, 10, 16, 30, 7, 31, 7, 7, 8, 7, 7, 34, 7, 23, 14, 36, 7

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OFFSET

1,1

COMMENTS

The sequence a(n) is an "even" supplement of the sequence A216066.

Does there exist an infinite set of solutions (in indices n in N) to each of the following three relations: a(n) + a(n+2) > a(n+1), a(n) + a(n+2) = a(n+1), and a(n) + a(n+2) < a(n+1)?

LINKS

Table of n, a(n) for n=1..72.

R. Witula and D. Slota, Fixed and periodic points of polynomials generated by minimal polynomials of 2cos(2Pi/n), International J. Bifurcation and Chaos, 19 (9) (2009), 3005.

CROSSREFS

Cf. A216066.

Sequence in context: A205782 A070296 A303581 * A072645 A316714 A135817

Adjacent sequences: A216644 A216645 A216646 * A216648 A216649 A216650

KEYWORD

nonn

AUTHOR

Roman Witula, Sep 12 2012

STATUS

approved