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Search: id:A117273
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| A117273 |
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Numbers n for which the product of the digits equals the number of prime numbers smaller than n. |
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+0
1
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| 16, 53, 63, 364, 437, 545, 573, 829, 963, 5449, 6475, 23797, 67458, 2475998
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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This sequence is finite with its largest term < 10^70. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 24 2006
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EXAMPLE
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364 is in the sequence because (1)the product of its digits is 3*6*4=72 and (2) there are 72 prime numbers smaller than 364.
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MATHEMATICA
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Select[Range[50000], DigitCount[ # ][[10]] == 0 && Product[i^DigitCount[ # ][[i]], {i, 1, 9}] == PrimePi[ # - 1] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 24 2006
g[n_] := Product[IntegerDigits[n][[m]], {m, 1, Length[IntegerDigits[n]]}]; Do[If[g[n] == PrimePi[n], Print[n]], {n, 1, 10000000}] - Mohammed Bouayoun (Mohammed.bouayoun(AT)sanef.com), Apr 24 2006
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CROSSREFS
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Cf. A000720
Sequence in context: A009936 A087701 A087973 this_sequence A137515 A164324 A137741
Adjacent sequences: A117270 A117271 A117272 this_sequence A117274 A117275 A117276
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KEYWORD
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base,more,nonn,fini
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AUTHOR
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Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006
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EXTENSIONS
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More terms from Zak Seidov (zakseidov(AT)yahoo.com), Stefan Steinerberger (stefan.steinerberger(AT)gmail.com) and Mohammed Bouayoun (Mohammed.bouayoun(AT)sanef.com), Apr 24 2006
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