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Search: id:A098685
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| A098685 |
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Numbers n such that pi(n)=sigma(d_1)*sigma(d_2)*...*sigma(d_k) where d_1 d_2 ... d_k is the decimal expansion of n. |
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+0
4
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| 15, 155, 252, 916, 1189, 12654, 55293, 177554, 418634, 753248, 885193
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Next term is greater than 10000000.
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EXAMPLE
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885193 is in the sequence because pi(885193)= sigma(8)*sigma(8)*sigma(5)*sigma(1)*sigma(9)*sigma(3).
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MATHEMATICA
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Do[d=IntegerDigits[n]; k=Length[d]; If[ !MemberQ[d, 0]&&PrimePi[n]== Product[DivisorSigma[1, d[[j]]], {j, k}], Print[n]], {n, 10000000}]
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CROSSREFS
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Cf. A098686, A098683, A098684.
Sequence in context: A125403 A010035 A017389 this_sequence A006096 A099915 A110557
Adjacent sequences: A098682 A098683 A098684 this_sequence A098686 A098687 A098688
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KEYWORD
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base,more,nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)math.ui.ac.ir), Sep 24 2004
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