%I #5 Aug 31 2013 17:13:19
%S 0,1,2,3,4,5,6,7,8,9,10,10,12,12,14,14,16,16,18,18,18,21,21,23,23,25,
%T 25,27,27,29,30,30,32,32,34,34,36,36,38,38,38,41,41,43,43,45,45,47,47,
%U 49,50,50,52,52,54,54,56,56,58,58,58,61,61,63,63,65,65
%N Largest number <= n with alternating parities of digits in decimal representation.
%C a(n) <= n <= A228723(n) and A228710(a(n)) = 1;
%C a(A030141(n)) = A030141(n); a(A228709(n)) < A228709(n).
%H Reinhard Zumkeller, <a href="/A228722/b228722.txt">Table of n, a(n) for n = 0..10000</a>
%e a(100) = 98; a(1000) = 989; a(10000) = 9898; a(100000) = 98989;
%e a(101) = 101; a(1001) = 989.
%o (Haskell)
%o a228722 n = head [x | x <- [n, n-1 ..], a228710 x == 1]
%K nonn,base
%O 0,3
%A _Reinhard Zumkeller_, Aug 31 2013