OFFSET
1,2
COMMENTS
For any pair of contiguous terms, one of the terms uses fewer digits than the other. This term is called the mask. Put the mask on the other term, starting from the left. What is not covered by the mask forms an odd number.
The sequence starts with a(1) = 1 and is always extended with the smallest integer not yet present that doesn't lead to a contradiction.
This sequence is a permutation of the integers > 0, as all integers will appear at some point, either as mask or masked.
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001
EXAMPLE
In the pair (1,11), 1 is the mask; 1 emerges and is odd;
In the pair (11,2), 2 is the mask; 1 emerges and is odd;
In the pair (2,13), 2 is the mask; 3 emerges and is odd;
In the pair (13,3), 3 is the mask; 3 emerges and is odd;
...
In the pair (11019,2018), 2018 is the mask; 9 emerges and is odd;
etc.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Apr 30 2018
STATUS
approved