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%I #8 Nov 21 2013 12:47:03
%S 69,169,269,369,469,569,669,690,769,869,969,1069,1169,1269,1369,1469,
%T 1569,1669,1690,1769,1869,1969,2069,2169,2269,2369,2469,2569,2669,
%U 2690,2769,2869,2969,3069,3169,3269,3369,3469,3569
%N Numbers n such that string 6,9 occurs in the base 10 representation of n but not of n-1.
%t Select[Range[4000],MemberQ[Partition[IntegerDigits[#],2,1],{6,9}] && !MemberQ[Partition[IntegerDigits[#-1],2,1],{6,9}]&] (* _Harvey P. Dale_, Jul 20 2011 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_