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A266819
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Expansion of Product_{k>=1} ((1 + x^k) * (1 + 2*x^k)).
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3
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1, 3, 5, 12, 20, 33, 60, 93, 144, 222, 340, 498, 729, 1050, 1486, 2115, 2946, 4068, 5592, 7608, 10278, 13854, 18483, 24528, 32426, 42594, 55677, 72498, 94008, 121290, 156002, 199842, 255012, 324438, 411318, 519771, 655128, 823056, 1031148, 1288590, 1605945
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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a(n) ~ c^(1/4) * exp(2*sqrt(c*n)) / (2*sqrt(6*Pi)*n^(3/4)), where c = Pi^2/4 + log(2)^2/2 + polylog(2, -1/2) = 2.259213400307794164599109607216595948859... .
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MATHEMATICA
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nmax = 50; CoefficientList[Series[Product[(1+x^k) * (1+2*x^k), {k, 1, nmax}], {x, 0, nmax}], x]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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