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Search: id:A143241
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| A143241 |
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Expansion of Product_{k>0} (1 - x^k) / (1 - x^(6*k - 2)). |
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1
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| 1, -1, -1, 0, 1, 0, -1, 1, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, -1, 0, 1, 0, -1, 0, 0, 0, 1, 1, -1, 0, 1, 0, 0, 0, -1, -1, 1, 1, 0, 0, -1, 0, 1, 0, -1, -1, 0, 0, 1, 0, -1, 0, 0, 0, 1, 0, -1, 0, 1, 0, 0, 1, -1, -1, 1, 0, 1, 0, -1, -1, 1, 1, -1, 1, 0, -1, 1, 1, 0, -1, -1, -1, 1, 1, -1, -1, 0, 0, 1, 1, -1, -1, 0, 0, 1, 1, -1, -1, 0, 0, 1, 1, -1, -2, 0
(list; graph; listen)
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OFFSET
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0,104
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COMMENT
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|a(n)|<2 if n<103, |a(n)|<3 if n<161.
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FORMULA
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Euler transform of period 6 sequence [ -1, -1, -1, 0, -1, -1, ...].
G.f.: Product_{k>0} (1 - x^k) / (1 - x^(6*k - 2)).
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EXAMPLE
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1 - q - q^2 + q^4 - q^6 + q^7 + q^8 - q^12 - q^18 + q^20 - q^22 + ...
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PROGRAM
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(PARI) {a(n) = if( n<0, 0, polcoeff( prod(k=1, n, (1 - x^k)^([1, 1, 1, 1, 0, 1][k%6 + 1]), 1 + x * O(x^n)), n))}
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CROSSREFS
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Sequence in context: A137979 A160338 A037281 this_sequence A118626 A062892 A118553
Adjacent sequences: A143238 A143239 A143240 this_sequence A143242 A143243 A143244
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KEYWORD
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sign
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AUTHOR
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Michael Somos, Aug 01 2008
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