%I #10 Jun 10 2016 00:20:59

%S 1,10,11,2,12,3,13,4,14,5,15,6,16,7,17,8,18,9,19,100,21,23,25,27,29,

%T 110,20,22,24,26,28,101,32,35,38,111,30,31,34,37,102,33,36,39,112,40,

%U 41,45,49,113,50,51,46,103,42,56,114,60,61,47,115,57,120,43,67,130,44,48,121

%N The digital sum of a(n) is visible in the smallest a(n+1) not yet present in the sequence.

%C a(1) = 1, and for n > 1 a(n) is the smallest integer not yet present in the sequence such that the digital sum of a(n-1) is a substring of the decimal digits of a(n).

%H Charles R Greathouse IV, <a href="/A173821/b173821.txt">Table of n, a(n) for n=1..10000</a>

%H Eric Angelini, <a href="http://www.cetteadressecomportecinquantesignes.com/DigitsumVIS.htm">Visible DigitSums</a> (sequence S)

%H E. Angelini, <a href="/A173821/a173821.pdf">Visible DigitSums</a> [Cached copy, with permission]

%e The digital sum of 1 is 1, so a(2) is the first unused number containing a "1", 10 (1 is already used). The digital sum of 10 is 1, so a(3) is the first unused number containing a "1", 11 (1 and 10 are already used)... The digital sum of 19 is 10, so a(20) is the first unused number containing a "10", 100 (10 is already used).

%Y Cf. A173822, A173823

%K base,nonn,look

%O 1,2

%A _Charles R Greathouse IV_ and _Eric Angelini_, Mar 01 2010