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A303398
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Expansion of Product_{k>=1} (1 - 3*x^k)/(1 + 3*x^k).
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3
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1, -6, 12, -24, 102, -312, 840, -2544, 7788, -23406, 69816, -208968, 628536, -1886712, 5654784, -16961856, 50900934, -152709936, 458084244, -1374231912, 4122828408, -12368549040, 37105252680, -111315549552, 333947845416, -1001844169854, 3005528872008
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) ~ c * (-3)^n, where c = QPochhammer[-1, -1/3]/QPochhammer[-1/3] = 1.1824106844873309732830080836112464096086... - Vaclav Kotesovec, Apr 25 2018
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MAPLE
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N:= 100: # for a(0)..a(N)
G:= mul((1-3*x^k)/(1+3*x^k), k=1..N):
S:= series(G, x, N+1):
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MATHEMATICA
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nmax = 30; CoefficientList[Series[Product[(1 - 3*x^k)/(1 + 3*x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Apr 25 2018 *)
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PROG
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(PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, (1-3*x^k)/(1+3*x^k)))
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CROSSREFS
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Expansion of Product_{k>=1} (1 - b*x^k)/(1 + b*x^k): A002448 (b=1), A303397 (b=2), this sequence (b=3), A303402 (b=4).
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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