[seqfan] Last digit is the difference

[Eric Angelini]

Hello Seqfans,

My friend Jean-Marc Falcoz has computed 10 000 terms of the hereunder 
sequence -- see the 10 000 terms and a (nice) graph there:
http://www.cetteadressecomportecinquantesignes.com/LastDigitIsDiff.htm 

> a(n) is the smallest integer not yet present in the sequence that has 
  two digits whose difference is the last digit of a(n-1); a(1) = 1.
 
S = 1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 90, 22,...

Example:
10 is the smallest integer not yet present in S that has two digits (1 and 0) 
whose difference (1) is the last digit of the previous term (1);

11 is the smallest integer not yet present in S that has two digits (1 and 1) 
whose difference (0) is the last digit of the previous term (0);

12 is the smallest integer not yet present in S that has two digits (1 and 2) 
whose difference (1) is the last digit of the previous term (1);

...
 
90 is the smallest integer not yet present in S that has two digits (9 and 0) 
whose difference (9) is the last digit of the previous term (9); etc.

Best,
É.