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A276720
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Number of set partitions of [n] such that for each block b the smallest integer interval containing b has at most four elements.
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6
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1, 1, 2, 5, 15, 37, 87, 208, 515, 1271, 3112, 7594, 18578, 45510, 111464, 272839, 667809, 1634784, 4002217, 9797781, 23985131, 58715973, 143739040, 351879841, 861416293, 2108779100, 5162371032, 12637686756, 30937555540, 75736343956, 185405513889, 453879917561
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OFFSET
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0,3
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LINKS
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FORMULA
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G.f.: -(x-1)*(x+1)/(x^8+3*x^7-5*x^5-5*x^4-x^3-2*x^2-x+1).
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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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