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Search: id:A102691
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| A102691 |
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Least n-expodigital number (i.e. numbers m such that m^n has exactly n digits). |
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+0
2
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| 0, 4, 5, 6, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n)= 10 - A102690(n).
10^(n-1) being the smallest n-digit number, n-expodigital numbers exist iff 10^(n-1) < 9^n,i.e.,iff n-1 < n*log_10(9);this condition holds for all n up to 21 because beyond we have, for instance,20 < 22*log_10(9) < 21. Thus numbers can be at most 21-expodigital.
Essentially the same as A067471. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 30 2008]
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EXAMPLE
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a(3)=5 because this is the first number followed by 6,7,8 and 9 which are all 3-expodigital:5^3=125; 6^3=216; 7^3=343; 8^3=512; 9^3=729.
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CROSSREFS
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Cf. A102690.
Sequence in context: A163875 A114546 A067471 this_sequence A014553 A121855 A090925
Adjacent sequences: A102688 A102689 A102690 this_sequence A102692 A102693 A102694
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KEYWORD
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fini,full,nonn
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AUTHOR
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Lekraj Beedassy (blekraj(AT)yahoo.com), Jan 21 2005
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