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a(1) = 1113; thereafter a(n) = (a(n-1) with digits sorted into descending order) - (a(n-1) with digits sorted into ascending order) (see the Kaprekar map, A151949).
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%I #8 May 10 2021 18:30:49

%S 1113,1998,8082,8532,6174,6174,6174,6174,6174,6174,6174,6174,6174,

%T 6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,

%U 6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174,6174

%N a(1) = 1113; thereafter a(n) = (a(n-1) with digits sorted into descending order) - (a(n-1) with digits sorted into ascending order) (see the Kaprekar map, A151949).

%H <a href="/index/K#Kaprekar_map">Index entries for the Kaprekar map</a>

%t NestList[FromDigits[Reverse[Sort[IntegerDigits[#]]]]-FromDigits[Sort[ IntegerDigits[ #]]]&,1113,40] (* or *) PadRight[{1113,1998,8082,8532},40,{6174}] (* _Harvey P. Dale_, May 10 2021 *)

%Y Cf. A099009, A151947, A151949, A151950, A069746.

%K nonn,base

%O 1,1

%A _N. J. A. Sloane_, Aug 18 2009