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A374609
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Numbers k such that k*(k+1) is primorial (a term in A002110).
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0
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OFFSET
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1,2
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COMMENTS
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All terms are squarefree numbers (A005117).
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LINKS
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FORMULA
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EXAMPLE
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714 is a term because 714*715 = 510510 = A002110(7) = 2*3*5*7*11*13*17.
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MATHEMATICA
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nn = 1000; MapIndexed[Set[P[First[#2]], #1] &, FoldList[Times, Prime@ Range[nn]]]; Monitor[Reap[Do[(d = Floor@ Sqrt[#]; If[Divisible[#, d], Sow[d]]) &[P[i]], {i, nn}]][[-1, 1]], i] (* Michael De Vlieger, Jul 14 2024 *)
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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STATUS
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approved
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