OFFSET
1,2
COMMENTS
The sequence starts with a(1) = 1 and was always extended with the smallest integer not yet present that does not lead to a contradiction.
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..6002
EXAMPLE
As a(1) = 1, we must have for a(2) an integer starting with an even digit; thus a(2) = 2, this integer being the smallest available one that does not lead to a contradiction; we extend then the sequence with a(3) = 3; this value "3" means that the next 3 digits must be even; we thus extend the sequence with a(4) = 4, a(5) = 6 and a(6) = 8; the next integer must start with an odd digit, thus a(7) = 5, which is the smallest available integer that doesn't lead to a contradiction; this value "5" means that the next 5 digits must be even; we thus extend the sequence with a(8) = 20, a(9) = 22 and a(10) = 21; etc.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Oct 19 2016
STATUS
approved