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A143277
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G.f.: Product_{k>0} (1 - x^(3*k))^2 / (1 - x^(3*k - 2)).
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0
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1, 1, 1, -1, 0, 0, -1, -2, -1, 1, -1, -2, 0, 0, -1, 0, 2, 1, -2, 0, 1, 1, 1, 2, 0, 1, 1, -1, -1, 2, 3, -1, 0, 2, -1, -1, 1, 1, -3, 0, 0, -1, 1, 2, 0, -3, -1, -2, -2, 1, 0, -1, 0, 0, -2, 0, 2, -2, -1, 0, -2, -2, 1, 1, -1, 2, 0, -2, 1, 2, -1, 0, 3, -2, -1, 2, -1, -3, 3, 2, -1, 3, 5, -1, -2, 1, 0, 0, 1, -1, 0, 2, 0, 0, 3, 1, -2, 0, 0, 0, 4, 2, -3, 1, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,8
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FORMULA
| Euler transform of period 3 sequence [ 1, 0, -2, ...].
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EXAMPLE
| 1 + q + q^2 - q^3 - q^6 - 2*q^7 - q^8 + q^9 - q^10 - 2*q^11 - q^14 + ...
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PROG
| (PARI) {a(n) = if( n<0, 0, polcoeff( prod(k=1, n, (1 - x^k)^([2, -1, 0][k%3 + 1]), 1 + x * O(x^n)), n))}
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CROSSREFS
| Sequence in context: A176250 A016541 A098876 * A056563 A088231 A143262
Adjacent sequences: A143274 A143275 A143276 * A143278 A143279 A143280
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KEYWORD
| sign
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AUTHOR
| Michael Somos, Aug 04 2008
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