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Search: id:A144261
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| A144261 |
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a(n) = smallest k such that k*n is a Niven (or Harshad) number. |
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+0
5
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| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 10, 1, 9, 3, 2, 3, 6, 1, 6, 1, 1, 5, 9, 1, 2, 6, 1, 3, 9, 1, 12, 6, 4, 3, 2, 1, 3, 3, 3, 1, 10, 1, 12, 3, 1, 5, 9, 1, 8, 1, 2, 3, 18, 1, 2, 2, 2, 9, 9, 1, 12, 6, 1, 3, 3, 2, 3, 3, 3, 1, 18, 1, 7, 3, 2, 2, 4, 2, 9, 1, 1, 5, 18, 1, 6, 6, 3, 3, 9, 1, 4, 5, 4, 9, 2, 2, 12, 4, 2, 1
(list; graph; listen)
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OFFSET
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1,11
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COMMENT
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Niven (or Harshad) numbers are numbers that are divisible by the sum of their digits.
Does a(n) exist for all n? - Klaus Brockhaus, Sep 19 2008
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LINKS
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Eric Weisstein's World of Mathematics, Harshad Number
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EXAMPLE
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a(14) = 3 since neither 1*14 or 2*14 are Niven numbers, but 3*14 = 42 is a Niven number: 42 = 7*(4+2).
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PROGRAM
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(PARI) digitsum(n) = {local(s=0); while(n, s+=n%10; n\=10); s} {for(n=1, 100, k=1; while((p=k*n)%digitsum(p)>0, k++); print1(k, ", "))} /* Klaus Brockhaus, Sep 19 2008 */
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CROSSREFS
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Cf. A005349 (Niven numbers), A144262 (smallest k such that k*n is not a Niven number), A144363 (records in A144261), A144364 (where records occur in A144261).
Sequence in context: A105162 A010184 A107830 this_sequence A046148 A164915 A010691
Adjacent sequences: A144258 A144259 A144260 this_sequence A144262 A144263 A144264
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KEYWORD
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base,nonn
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AUTHOR
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Sergio Pimentel (ferdiego(AT)suddenlink.net), Sep 16 2008
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EXTENSIONS
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Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Sep 19 2008
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