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Each odd digit "k" is followed by k even digits.
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%I #11 Oct 31 2016 05:12:36

%S 1,2,3,4,6,8,5,20,22,21,23,24,25,26,28,27,40,42,44,29,46,48,60,62,41,

%T 43,64,45,66,68,47,80,82,84,49,86,88,200,201,61,63,202,7,204,206,65,

%U 208,203,220,9,222,224,226,10,12,14,16,18,30,205,228,207,240,242,67,244,246,69,248,260,262,32,209,264,266,268

%N Each odd digit "k" is followed by k even digits.

%C 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.

%H Jean-Marc Falcoz, <a href="/A277519/b277519.txt">Table of n, a(n) for n = 1..6002</a>

%e 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.

%Y Cf. A277518.

%K nonn,base

%O 1,2

%A _Eric Angelini_ and _Jean-Marc Falcoz_, Oct 19 2016