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Search: id:A131904
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| A131904 |
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Smallest positive integer k with the same number of divisors as the n-th integer for which such a k exists. |
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+0
1
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| 2, 2, 2, 6, 4, 6, 2, 2, 6, 6, 2, 12, 2, 12, 6, 6, 2, 4, 6, 6, 12, 2, 24, 2, 12, 6, 6, 6, 2, 6, 6, 24, 2, 24, 2, 12, 12, 6, 2, 4, 12, 6, 12, 2, 24, 6, 24, 6, 6, 2, 2, 6, 12
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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a(n)=min(k>0, k has the same number of divisors as A131903(n))
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EXAMPLE
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a(4)=6 because A131903(n)=8 which has got four divisors and 6 is the least positive integer with four divisors
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MATHEMATICA
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Clear[tmp]; Function[n, If[Head[ #1] === tmp, #1 = n; Unevaluated[Sequence[]], # ] & [tmp[DivisorSigma[0, n]]]] /@ Range[64]
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CROSSREFS
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Cf. A069822, A131902-A131908.
Adjacent sequences: A131901 A131902 A131903 this_sequence A131905 A131906 A131907
Sequence in context: A119918 A084867 A099259 this_sequence A038074 A059885 A097091
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KEYWORD
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easy,nonn
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AUTHOR
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Peter Pein (petsie(AT)dordos.net), Jul 26 2007
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