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A180011
a(n) = smallest k > 1 such that n and kn have the same digit sum
1
10, 10, 4, 10, 10, 4, 10, 10, 2, 10, 10, 10, 10, 10, 4, 10, 10, 2, 10, 10, 10, 10, 10, 10, 10, 10, 2, 10, 10, 4, 10, 10, 4, 10, 10, 2, 10, 10, 4, 10, 10, 10, 10, 10, 2, 10, 10, 4, 10, 10, 4, 10, 10, 2, 10, 10, 4, 10, 10, 4, 10, 10, 2, 10, 10, 4, 10, 10, 4, 10, 10, 2, 10, 10, 7, 10, 10
OFFSET
1,1
COMMENTS
2 <= a(n) <= 10
Every number from 2 through 10 is in the sequence. a(9) = 2, a(144) = 3, a(3) = 4, a(243) = 5, a(5553) = 6, a(75) = 7, a(1314) = 8, a(6876) = 9, a(1) = 10. n !== 0 (mod 3) ==> a(n) = 10
LINKS
MAPLE
Digit sum of 15 = 6. The next multiple of 15 with digit sum 6 = 4*15 = 60, so a(15) = 4.
MATHEMATICA
ds[n_]:=Module[{dsn=Total[IntegerDigits[n]], k=2}, While[dsn!=Total[ IntegerDigits[k n]], k++]; k]; Array[ds, 80] (* Harvey P. Dale, Jan 16 2012 *)
CROSSREFS
Sequence in context: A360207 A228245 A034078 * A275626 A071531 A276467
KEYWORD
base,easy,nonn
AUTHOR
David W. Wilson, Aug 06 2010
STATUS
approved