A276105 - OEIS

%I #10 Dec 01 2019 23:13:30

%S 1,2,3,4,20,5,21,6,23,7,24,8,25,9,26,12,10,27,32,11,28,42,13,29,52,14,

%T 200,201,203,204,205,206,207,208,209,210,211,213,214,215,216,217,218,

%U 219,230,231,233,234,235,236,237,238,239,240,241,243,244,245,246,247,248,249

%N Lexicographically first sequence (with no duplicate term) where all the digits "2" are separated by two digits.

%C The sequence is started with a(1)=1 and always extended with the smallest integer not yet used that does not lead to a contradiction.

%e To match the infinite digit-pattern 2..2..2..2..2..2.. (etc.) one must use the integer 20 after the fourth term (which is 4), then use the integer 5, then use the integer 21, then use the integer 6, then use the integer 23 (as 22 is forbidden: no integer with consecutive 2's is allowed), etc.

%K nonn,base

%O 1,2

%A _Eric Angelini_, Aug 18 2016