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%I A277998 #6 Nov 08 2016 07:37:04
%S A277998 1,9,11,91,92,8,2,81,93,7,3,71,94,6,4,61,95,5,51,96,41,97,31,98,21,99,
%T A277998 12,82,83,72,84,62,85,52,86,42,87,32,88,22,89,13,73,74,63,75,53,76,43,
%U A277998 77,33,78,23,79,14,64,65,54,66,44,67,34,68,24,69,15,55,56,45,57,35,58,25,59,16,46,47,36,48,26,49,17,37,38,27,39,18,28,29,19,101,901,902,801,903,701,904,601,905,501,906,401,907,301,908,201
%N A277998 Lexicographically first sequence (with no duplicates) where the last digit of a(n) added to the first digit of a(n+1) equals 10.
%C A277998 The sequence starts with a(1) = 1 and was always extended with the smallest integer not yet present that does not lead to a contradiction.
%H A277998 Jean-Marc Falcoz, <a href="/A277998/b277998.txt">Table of n, a(n) for n = 1..10001</a>
%e A277998 The sequence begins with 1, 9, 11, 91, 92, 8, 2, 81, 93, 71... The two digits that border the first comma are 1 and 9 that sum up to 10 as required; the 2nd comma is bordered by 9 and 1; the 3rd one by 1 and 9 again; the 4th one by 1 and 9 too; the 5th one by 2 and 8; the 6th one by 8 and 2; the 7th one by 2 and 8 again; the 8th one by 1 and 9; the 9th one by 3 and 7, etc.
%K A277998 nonn,base
%O A277998 1,2
%A A277998 _Eric Angelini_ and _Jean-Marc Falcoz_, Nov 08 2016

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