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%I #14 Mar 08 2019 03:35:03
%S 0,1,2,20,21,3,23,4,5,6,7,8,9,10,11,13,14,15,16,12,17,18,19,30,31,33,
%T 34,35,36,37,32,38,42,39,40,41,43,44,45,46,47,48,49,50,52,51,53,24,54,
%U 55,25,56,57,62,58,59,60,72,61,63,64,65,26,66,67,68,69,27,70,71,73,74,82,75,76,77,78,79,92,80,81,83,84,85,86,120,87,88,89,90,91,93,121,94,95,96,97,98,99,102,100,101,103,104,105,123,106,107,108,112,109,110,111,113,114,132,115,116,117,118,119,130,28
%N The successive numbers of digits between two "2"s in the sequence are given by the sequence itself.
%C This is the lexicographically first such sequence, starting with a(1)=0, that has always been extended with the smallest integer not already present in the sequence and not leading to a contradiction.
%e There are 0 digits between the first two "2"s of the sequence: [0,1,2,20]; there is 1 digit between the next pair of "2"s: [20,21]; there are 2 digits between the next pair of "2"s: [21,3,23]; there are 20 digits between the next pair of "2"s: [23,4,5,6,7,8,9,10,11,13,14,15,16,12]; etc. The numbers 0, 1, 2, 20,... rebuild the starting sequence.
%K nonn,base
%O 1,3
%A _Eric Angelini_ and _Lars Blomberg_, May 23 2016
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