Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #15 Sep 15 2016 07:46:57
%S 0,1,3,2,5,7,4,9,11,10,13,15,17,6,19,8,31,33,35,21,14,37,22,23,30,39,
%T 25,34,41,12,27,50,51,29,53,16,55,43,32,57,44,45,36,59,47,52,71,49,56,
%U 61,18,73,63,38,75,65,54,77,66,67,58,79,69,74,91,93,81,76,95,83,96,97,85,99,94,111,70,112,110,113,115,118
%N Between two successive even digits "a" and "b" there are exactly |a-b| odd digits.
%C The sequence is started with a(1) = 0 and always extended with the smallest unused integer not leading to a contradiction.
%C The sequence is not a permutation of the natural numbers as 42, for instance, will never appear (according to the definition, 42 should show |4-2| odd digits between " 4 " and " 2 " and shows none).
%H Jean-Marc Falcoz, <a href="/A276684/b276684.txt">Table of n, a(n) for n = 1..10004</a>
%e Between the first 0 and the first 2 of the sequence, there are indeed |0-2| = 2 odd digits (1 and 3).
%e Between the first 2 and the first 4 of the sequence, there are indeed |2-4| = 2 odd digits (5 and 7).
%e Between the first 4 and the second 0 of the sequence, there are indeed |4-0| = 4 odd digits (9,1,1 and 1).
%e Between the second 0 and the first 6 of the sequence, there are indeed |0-6| = 6 odd digits (1,3,1,5,1 and 7).
%e Between the first 6 and the first 8 of the sequence, there are indeed |6-8| = 2 odd digits (1 and 9).
%K nonn,base
%O 1,3
%A _Eric Angelini_ and _Jean-Marc Falcoz_, Sep 13 2016