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Take the n-th pair of consecutive digits of the sequence and form their absolute difference; the result is the n-th digit of the sequence; a(n) < a(n+1).
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%I #7 Mar 31 2012 13:46:51

%S 1,2,3,5,6,9,16,17,90,98,170,181,901,1090,8010,70001,80010,90001,

%T 98000,98808,99011,107001,111010,800000,1000900,1100010,9080000,

%U 9909080,80008090,90001010,100070000,100101011,101000800,110000000,111000009

%N Take the n-th pair of consecutive digits of the sequence and form their absolute difference; the result is the n-th digit of the sequence; a(n) < a(n+1).

%C Start with a(1) = 1. In general choose a(n) to be the smallest number consistent with a(i) (for i < n) and the other requirements.

%e First pair of digits is [12]; absolute difference = 1; 1 is the first digit of the sequence.

%e 2nd pair of digits is [35]; absolute difference = 2; 2 is the 2nd digit of the sequence.

%e 3rd pair of digits is [69]; absolute difference = 3; 3 is the 3rd digit of the sequence.

%e 4th pair of digits is [16]; absolute difference = 5; 5 is the 4th digit of the sequence.

%K base,easy,nonn

%O 1,2

%A _Eric Angelini_, Feb 04 2005, in collaboration with Hugo van der Sanden, Jacques Tramu, Frederic Zgud and Marc Seguin.

%E Minor edits by _N. J. A. Sloane_, Jan 24 2008