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Search: id:A064023
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| A064023 |
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Smallest prime m such that prod(m)=n*l(m)*sum(m) where prod(m) is the product of the digits of m, l(m) is the number of digits of m, sum(m) is the sum of the digits of m; or 0 if no such m exists. |
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+0
2
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| 2, 347, 5861, 225461, 55541, 4583, 4457, 117883, 15559, 151687, 0, 155383, 0, 5857, 118589, 126487, 0, 4789, 0, 134587, 7687, 0, 0, 25867, 165457, 0, 34759, 182687, 0, 38557, 0, 44587, 0, 0, 45757, 25889, 0, 0, 0, 244567, 0, 148667, 0, 0, 225689, 0, 0
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If n is divisible by a prime larger than 7, then n can't divide prod(m), so a(n)=0. Are there any other values of n with a(n)=0?
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EXAMPLE
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a(2)=347 because prod(347)=84, sum(347)=14, l(347)=3, n=2 and 84=2*3*14
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MATHEMATICA
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id := IntegerDigits; prod[n_] := Times@@id[n]; l[n_] := Length[id[n]]; sum[n_] := Plus@@id[n]; a[n_] := If[FactorInteger[2n][[ -1, 1]]>7, 0, For[k=1, True, k++, m=Prime[k]; If[prod[m]==n*l[m]sum[m], Return[m]]]]
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CROSSREFS
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Cf. A064022.
Sequence in context: A063968 A064501 A063831 this_sequence A024350 A012669 A062381
Adjacent sequences: A064020 A064021 A064022 this_sequence A064024 A064025 A064026
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KEYWORD
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nonn,base
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AUTHOR
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Felice Russo (felice.russo(AT)katamail.com), Sep 18 2001
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EXTENSIONS
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Edited by Dean Hickerson (dean(AT)math.ucdavis.edu), Jun 02 2002
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