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Search: id:A104862
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| 0, 1, 1, 1, 1, 0, -2, -5, -9, -13, -15, -12, 0, 25, 65, 117, 169, 196, 158, 3, -321, -841, -1519, -2200, -2560, -2079, -79, 4121, 10881, 19720, 28638, 33435, 27351, 1547, -52895, -140772, -256000, -372775, -436655, -359763, -26871
(list; graph; listen)
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OFFSET
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0,7
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COMMENT
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Real part of the sequence of complex numbers defined by c(0) = 1, c(1) = 1, for n>1 c(n) = c(n-1) + i*c(n-2).
a(n) = real part of the sequence b of quaternions defined by b(0)=1,b(1)=1, b(n) = b(n-1) + b(n-2)*(0,s,s,s) where s = 1/sqrt(3).
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FORMULA
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G.f.: Re(1/(1-x-ix^2))=(1-x)/(1-2x+x^2+x^4). - Paul Barry (pbarry(AT)wit.ie), Apr 25 2005
a(n)=sum{k=0..floor(n/2), C(n-k, k)cos(pi*k/2)}; - Paul Barry (pbarry(AT)wit.ie), Apr 25 2005
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CROSSREFS
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Cf. A014292.
Sequence in context: A070828 A112988 A139405 this_sequence A114471 A060636 A050877
Adjacent sequences: A104859 A104860 A104861 this_sequence A104863 A104864 A104865
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KEYWORD
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sign
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AUTHOR
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Gerald McGarvey (gerald.mcgarvey(AT)comcast.net), Apr 24 2005
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