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A165207
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Period length 4: repeat 2, 2, 4, 4.
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3
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2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| Continued fraction expansion of (21+5*sqrt(26))/19 = A177153. [From Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 03 2010]
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FORMULA
| a(n)=2*A130658(n).
a(n) = A002378(n+1)/A064038(n+2) = A061037(4n+6)/A064038(n+2) = A061037(4n+6)/A061041(8n+12).
a(n) = a(n-1)-a(n-2)+a(n-3). G.f.: 2*(1+2*x^2)/((1-x)*(1+x^2)) [R. J. Mathar, Sep 11 2009]
a(n)=3-[(1/2)-(1/2)*I]*I^n-[(1/2)+(1/2)*I]*(-I)^n, with n>=0 and I=sqrt(-1). a(n)=(1/2)*{2*(n mod 4)+[(n+1) mod 4]+[(n+3) mod 4]}, with n>=0. [From Paolo P. Lava (paoloplava(AT)gmail.com), Sep 16 2009]
a(n) = 3-cos(Pi*n/2)-sin(Pi*n/2). - R. J. Mathar, Oct 08 2011
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CROSSREFS
| Sequence in context: A097860 A098979 A071928 * A130501 A049116 A065176
Adjacent sequences: A165204 A165205 A165206 * A165208 A165209 A165210
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KEYWORD
| nonn,easy
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AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Sep 07 2009
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EXTENSIONS
| Edited, offset set to 0, by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 11 2009
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