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First monotonically increasing sequence such that erasing the first and last digit of each term and concatenating what is left results in the concatenation of all terms of the sequence.
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%I #11 Aug 09 2012 15:29:11

%S 110,111,200,210,211,212,220,300,400,420,510,600,620,710,711,720,810,

%T 820,822,823,900,930,1000,1400,2040,2200,2510,3060,4000,4620,5070,

%U 6100,6710,7170,7200,7810,8080,8200,9280,12390,20090,23010

%N First monotonically increasing sequence such that erasing the first and last digit of each term and concatenating what is left results in the concatenation of all terms of the sequence.

%C Could one say this is kind of fractal?

%e To avoid numbers beginning with 0, we assume the first term is 1xy, and so x=1, so 11y, but y=0 works, so the first term is 110.

%e The next two terms must be a1b, c0d, and se we take a=b=1, c=2, d=0, so now the sequence begins 110, 111, 200. And so on.

%Y Cf. A106003.

%K base,easy,nonn

%O 1,1

%A _Eric Angelini_, Apr 29 2005