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0, 1, 2, 3, 4, 6, 7, 11, 15, 18, 23, 27
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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COMMENTS
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All numbers less than 2.5*10^15 in Sylvester's sequence are squarefree and no squareful numbers in this sequence are known (Vardi 1991).
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REFERENCES
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Vardi, I. "Are All Euclid Numbers Squarefree?" and "PowerMod to the Rescue." Sections 5.1 and 5.2 in Computational Recreations in Mathematica. Reading, MA: Addison-Wesley, pp. 82-89, 1991.
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LINKS
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FORMULA
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MATHEMATICA
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PrimeNu[NestList[#^2 - # + 1 &, 2, 10] - 1] (* G. C. Greubel, May 09 2017 *)
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CROSSREFS
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KEYWORD
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hard,more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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