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A014695
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Poincare series (or Molien series) for mod 2 cohomology of Q_8.
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12
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1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Contribution from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 14 2010: (Start)
Periodic sequence: Repeat 1, 2, 2, 1.
a(n) = A130658(n+1).
Continued fraction expansion of (5+sqrt(221))/14.
Decimal expansion of 37/303. (End)
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REFERENCES
| A. Adem, Recent developments in the cohomology of finite groups, Notices Amer. Math. Soc., 44 (1997),806-812.
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LINKS
| Eric Weisstein's World of Mathematics, Simple Graph
Index entries for Molien series
Index to sequences with linear recurrences with constant coefficients, signature (1,-1,1).
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FORMULA
| G.f.: (1+x+x^2)/((1-x)*(1+x^2)) = (1+2*x+2*x^2+x^3)/(1-x^4).
a(n)=(3-sqrt(2)*cos((2*n+1)*Pi/4))/2 [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Nov 28 2009]
a(n) = (6-(1+I)*I^n-(1-I)*(-I)^n)/4 where I = sqrt(-1). [From Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 14 2010]
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CROSSREFS
| Denominators for the sequence whose numerators are A064038.
Cf. A130658, A177841. [From Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 14 2010]
Sequence in context: A073783 A134430 A130658 * A071017 A112049 A055230
Adjacent sequences: A014692 A014693 A014694 * A014696 A014697 A014698
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 14 2010
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