%I
%S 12,112,120,212,312,412,512,612,712,812,912,1012,1112,1120,1200,1312,
%T 1412,1512,1612,1712,1812,1912,2012,2112,2120,2212,2312,2412,2512,
%U 2612,2712,2812,2912,3012,3112,3120,3212,3312,3412
%N Numbers n such that string 1,2 occurs in the base 10 representation of n but not of n1.
%t Select[Range[3500],MemberQ[Partition[IntegerDigits[#],2,1],{1,2}] && !MemberQ[ Partition[IntegerDigits[#1],2,1],{1,2}]&] (* _Harvey P. Dale_, Jul 13 2014 *)
%K nonn,base
%O 1,1
%A _Clark Kimberling_
