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%I #2 Mar 30 2012 17:26:16
%S 1,2,3,4,5,6,7,8,9,1,11,21,13,41,15,61,17,81,19,20,21,22,23,24,25,26,
%T 27,28,29,3,31,23,33,43,35,63,37,83,39,40,41,42,43,44,45,46,47,48,49,
%U 5,51,25,53,45,55,65,57,85,59,60,61,62,63,64,65,66,67,68,69,7,71,27,73,47,75
%N In the natural numbers, swap digits in pairs (even-odd).
%C Differs from A000027 and A107602 starting with a(10)=1.
%e 0 is even hence n = 10 => 1, n=100=>10, etc.
%Y Cf. A000027, A107602.
%K nonn,base
%O 1,2
%A _Zak Seidov_, May 17 2005