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%I #7 Jul 26 2016 06:15:04
%S 1,2,3,4,6,5,7,8,20,9,10,22,21,11,12,24,26,23,13,14,28,40,15,16,42,44,
%T 46,17,18,48,60,62,25,19,30,64,66,68,80,82,84,86,88,200,31,32,202,204,
%U 201,33,34,206,208,220,35,36,222,224,226,228,240,242,244,37,38,246,248,260,262,264,266,203,39,50,268,280,282,27,51,52,284,286,288,205,53,54,400,402,404,406
%N The even digits in the sequence appear in blocks and the successive sizes of these blocks are given by the sequence itself.
%C This is the lexicographically first such sequence starting with a(1)=1 and being always extended with the smallest integer not yet present that doesn't lead to a contradiction.
%H Jean-Marc Falcoz, <a href="/A275376/b275376.txt">Table of n, a(n) for n = 1..1001</a>
%e The blocks of even digits are indicated here by parentheses; the successive block-sizes are 1, 2, 3, 4, 6, 5,... which reproduces the sequence itself:
%e 1,(2),3,(4,6),5,7,(8,20),9,1(0,22,2)1,11,1(2,24,26,2)3,13,1(4,28,40),15...
%K nonn,base
%O 1,2
%A _Eric Angelini_ and _Jean-Marc Falcoz_, Jul 25 2016