A106003 - OEIS

%I #8 Aug 09 2012 15:30:33

%S 0,1,2,3,4,5,6,7,8,9,110,111,200,210,211,212,220,300,400,420,510,600,

%T 620,710,711,720,810,820,822,823,900,930,10000,10001,10400,11000,

%U 11001,11400,12200,13000,13500,14100,15000,15600,16000,16001,16600,17200

%N Keep only the middle digit of each integer and concatenate them. The result is the concatenation of all integers of the sequence.

%C Could one say this is kind of fractal?

%C The definition seems to be the following: all terms have an odd number of digits, and are strictly increasing. Now delete all except the middle digits of each term. The result is the succession of digits of all the terms. We take the lexicographically earliest sequence satisfying these conditions. - _N. J. A. Sloane_, Aug 09 2012

%Y Cf. A106004.

%K base,easy,nonn

%O 0,3

%A _Eric Angelini_, Apr 29 2005