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Search: id:A097117
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| A097117 |
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Expansion of (1+x)/((1-x)^2-4*x^3). |
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+0
1
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| 1, 1, 1, 5, 13, 25, 57, 141, 325, 737, 1713, 3989, 9213, 21289, 49321, 114205, 264245, 611569, 1415713, 3276837, 7584237, 17554489, 40632089, 94046637, 217679141, 503840001, 1166187409, 2699251381, 6247675357, 14460848969, 33471028105
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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Related to the Lorenz-Poincare geometry of the group PSL[2,C]. - Roger Bagula (rlbagulatftn(AT)yahoo.com), Feb 17 2006
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FORMULA
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G.f. : (1+x)/(1-2x+x^2-4x^3); a(n)=2a(n-1)-a(n-2)+4a(n-3); a(n)=sum{k=0..floor(n/2), binomial(n-k, 2k)4^k }.
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MATHEMATICA
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M = {{0, 1, 0}, {0, 0, 1}, {4, -1, 2}}; w[0] = {0, 1, 1}; w[n_] := w[n] = M.w[n - 1] a = Flatten[Table[w[n][[1]], {n, 0, 25}]] - Roger Bagula (rlbagulatftn(AT)yahoo.com), Feb 17 2006
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CROSSREFS
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Sequence in context: A147427 A147408 A147090 this_sequence A146140 A146283 A026373
Adjacent sequences: A097114 A097115 A097116 this_sequence A097118 A097119 A097120
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jul 25 2004
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Aug 14 2008
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