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Search: id:A064156
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| A064156 |
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Smallest prime with n decimal digits such that the product of its digits equals n times the sum of its digits, or 0 if no such prime exists. |
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+0
1
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| 2, 0, 167, 1427, 0, 126241, 1111457, 12222241, 111113543, 0, 0, 111111118273, 0, 0, 111111111126581, 1111111111144841, 0, 111111111111126443, 0, 11111111111122225421, 111111111111111135781, 0, 0, 111111111111111111244561, 1111111111111111121255521, 0, 111111111111111111111113797
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Max Alekseyev, Table of n, a(n) for n=1..200
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EXAMPLE
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167 belongs to the sequence because this is the smallest prime with 3 digits such that 1*6*7=42 and 3*(1+6+7)=42
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MATHEMATICA
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NextPrim[ n_ ] := (k = n + 1; While[ ! PrimeQ[ k ], k++ ]; k); Do[ If[ n != 1 && Transpose[ FactorInteger[ n ] ][ [ 1, -1 ] ] <= 10, k = NextPrim[ (10^n - 1)/9 ];
While[ d = IntegerDigits[ k ]; k < 10^n && n*Apply[ Plus, d ] != Apply[ Times, d ], k = NextPrim[ k ] ]; If[ k < 10^n, Print[ k ], Print[ 0 ] ], If[ n == 1, Print[ 2 ], Print[ 0 ] ] ], {n, 1, 9} ]
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CROSSREFS
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Adjacent sequences: A064153 A064154 A064155 this_sequence A064157 A064158 A064159
Sequence in context: A003321 A012333 A012329 this_sequence A013555 A012335 A012331
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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 14 2001
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EXTENSIONS
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Corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 05 2001
a(14), a(20), a(25) and b-file from Max Alekseyev (maxale(AT)gmail.com), May 07 2009
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