login
Numbers n such that string 4,7 occurs in the base 10 representation of n but not of n-1.
0

%I #7 Nov 29 2012 15:07:31

%S 47,147,247,347,447,470,547,647,747,847,947,1047,1147,1247,1347,1447,

%T 1470,1547,1647,1747,1847,1947,2047,2147,2247,2347,2447,2470,2547,

%U 2647,2747,2847,2947,3047,3147,3247,3347,3447,3470

%N Numbers n such that string 4,7 occurs in the base 10 representation of n but not of n-1.

%t Select[Range[4000],MemberQ[Partition[IntegerDigits[#],2,1],{4,7}] && !MemberQ[Partition[IntegerDigits[#-1],2,1],{4,7}]&] (* _Harvey P. Dale_, Nov 29 2012 *)

%K nonn,base

%O 1,1

%A _Clark Kimberling_