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A002998
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Smallest multiple of n whose digits sum to n.
(Formerly M0489)
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16
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 190, 209, 48, 247, 266, 195, 448, 476, 198, 874, 3980, 399, 2398, 1679, 888, 4975, 1898, 999, 7588, 4988, 39990, 8959, 17888, 42999, 28798, 57995, 29988, 37999, 59888, 49998, 699880, 177899, 88998, 99889, 479996, 499995
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OFFSET
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0,3
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COMMENTS
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The subsequence of repdigits is: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 888, 999, 999999999, 999999999999999999999999999, ... and their indices are: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 24, 27, 81, 243, 729, 999, ... - Michel Marcus, Apr 14 2015
a(n) is the smallest harshad number (see A005349) whose sum of digits is n; it is not obvious that a(n) exists for all n, see Mohammed Aassila's reference. - Robert FERREOL, Jun 30 2023
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REFERENCES
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Mohammed Aassila, 1000 challenges mathématiques, Algèbre, Ellipses, 2016, p. 110.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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H. Fredricksen, E. J. Ionascu, F. Luca, and P. Stanica, Minimal Niven numbers, arXiv:0803.0477 [math.NT], 2008.
H. Fredricksen, E. J. Ionascu, F. Luca, and P. Stanica, Minimal Niven numbers, Acta Arithmetica 132(2008), 135-159.
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MATHEMATICA
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Flatten[Table[Select[n Range[100000], Total[IntegerDigits[#]] == n&, 1], {n, 0, 50}]] (* Harvey P. Dale, Oct 30 2011 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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