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A144437
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Period length 3: 3,3,1 (repeat).
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11
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3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1, 3, 3, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The sequence is generated from numerators in the energy differences of the hydrogen spectrum:
A005563(1), A061037(4), A061039(6), A061041(8), A061043(10), A061045(12), A061047(14), A061049(16), ...
Conjecture: a(n) is the separatix. See A045944.
Also the decimal expansion of the constant 3310/999. [R. J. Mathar, May 21 2009]
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (0,0,1).
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FORMULA
| a(n)=(7-4*cos(2*pi*n/3))/3 [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Nov 23 2008]
a(n)=(1/9)*{(n mod 3)+13*[(n+1) mod 3]+7*[(n+2) mod 3]}, with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Nov 27 2008]
G.f.: -x*(3+3*x+x^2)/((x-1)*(1+x+x^2)) - [R. J. Mathar, May 21 2009]
a(n) = 3/GCD(n,3). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 30 2009]
a(n)=denominator(n^k/3), where k>0 is an integer, Enrique Pérez Herrero, Oct 05 2011
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MATHEMATICA
| A144437[n_]:=Denominator[n/3]; Array[A144437, 100] (* Enrique Pérez Herrero, Oct 05 2011 *)
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CROSSREFS
| Cf. A164306, A167192, A109007. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 30 2009]
Sequence in context: A088420 A103585 A154595 * A169609 A138071 A206400
Adjacent sequences: A144434 A144435 A144436 * A144438 A144439 A144440
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KEYWORD
| nonn,easy
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AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Oct 05 2008
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EXTENSIONS
| Edited by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 21 2009
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