OFFSET
0,3
COMMENTS
a(n) = A131382(n) * n. - Michel Marcus, Dec 10 2012
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
REFERENCES
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).
LINKS
David Wilson, Table of n, a(n) for n = 0..1000
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.
H. W. Gould, Letters to N. J. A. Sloane, 1974
David Wilson, C++ program
MATHEMATICA
Flatten[Table[Select[n Range[100000], Total[IntegerDigits[#]] == n&, 1], {n, 0, 50}]] (* Harvey P. Dale, Oct 30 2011 *)
PROG
(PARI) a(n)=my(k); while(sumdigits(k+=n)!=n, ); k \\ Charles R Greathouse IV, Feb 01 2013
CROSSREFS
KEYWORD
nonn,base,easy,nice
AUTHOR
EXTENSIONS
More terms from Erich Friedman, Jul 04 2001
STATUS
approved