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Search: id:A010673
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| 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Euler number (or Euler characteristic) of (n+1)-sphere. - Franz Vrabec (franz.vrabec(AT)aon.at), Sep 07 2007
Submitted A153735=-1,0,0,2,4,10,20,. a(n+1)=A153735(n+1)-2*A153735(n). [From Paul Curtz (bpcrtz(AT)free.fr), Jan 01 2009]
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REFERENCES
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R. Carter, G. Segal, I. Macdonald, Lectures on Lie Groups and Lie Algebras, London Mathematical Society Student Texts 32, Cambridge University Press, 1995; see p. 68.
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FORMULA
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1-(-1^n).
a(n)=2*(n mod 2) - Paolo P. Lava (ppl(AT)spl.at), Oct 20 2006
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CROSSREFS
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Sequence in context: A096972 A101227 A021499 this_sequence A084099 A036665 A053472
Adjacent sequences: A010670 A010671 A010672 this_sequence A010674 A010675 A010676
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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