OFFSET
1,1
COMMENTS
Define the digital mean of n in base b, dm(b, n), to be (Sum_{i=1..d} 2*d_i - (b-1)) / (2*d), where d is the number of digits in the base b representation of n and d_i the individual digits.
a(n) is the subset of multiples of nine for which dm(10, n) = 0; that is, two times the sum of the digits is equal to nine times the number of digits.
LINKS
Paolo Xausa, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[200]*9, 2*DigitSum[#] == 9*IntegerLength[#] &] (* Paolo Xausa, May 17 2024 *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Reikku Kulon, Sep 21 2008
STATUS
approved