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A275100
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Number of set partitions of [3*n] such that within each block the numbers of elements from all residue classes modulo n are equal for n>0, a(0)=1.
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2
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1, 5, 16, 64, 298, 1540, 8506, 48844, 286498, 1699300, 10136746, 60643324, 363328498, 2178376660, 13065476986, 78378513004, 470228031298, 2821239047620, 16927046865226, 101561118929884, 609363226794898, 3656168900416180, 21936982021437466, 131621797985445964
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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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G.f.: -(21*x^3-7*x^2-5*x+1)/((x-1)*(6*x-1)*(3*x-1)).
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MATHEMATICA
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CoefficientList[Series[-(21x^3-7x^2-5x+1)/((x-1)(6x-1)(3x-1)), {x, 0, 30}], x] (* Harvey P. Dale, Dec 15 2018 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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