OFFSET
1,3
COMMENTS
The sequence is started with a(1) = 1 and always extended with the smallest unused integer not leading to a contradiction.
The sequence is not a permutation of the natural numbers as 31, for instance, will never appear (according to the definition, 31 should show |3-1| = 2 even digits between " 3 " and " 1 " and doesn't).
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..10004
EXAMPLE
Between the first 1 and the first 3 of the sequence, there are indeed |1-3| = 2 even digits (0 and 2).
Between the first 3 and the first 5 of the sequence, there are indeed |3-5| = 2 even digits (4 and 6).
Between the first 5 and the second 1 of the sequence, there are indeed |5-1| = 4 even digits (8,2,0 and 2).
Between the second 1 and the third 1 of the sequence, there are indeed |1-1| = 0 even digits.
Between the third 1 and the first 9 of the sequence, there are indeed |1-9| = 8 even digits (0,2,2,2,4,2,6 and 2).
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Sep 13 2016
STATUS
approved