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Least number that requires exactly n iterations of f(x) = reverse(x) - maxdigit(x) to reach zero.
5

%I #6 Dec 15 2017 17:36:45

%S 1,11,16,12,15,25,36,106,104,108,197,1009,1022,1052,1091,1073,1801,

%T 10004,10005,10051,10062,10071,10083,10081,10092,14991,19982,19991,

%U 100092,100192,100282,100191,107991,101973,289101,1000094,1000084

%N Least number that requires exactly n iterations of f(x) = reverse(x) - maxdigit(x) to reach zero.

%e a(5)=15 because 15 -> 46 -> 58 -> 77 -> 70 -> 0 takes five steps to reach zero.

%t g[n_] := Block[{id = IntegerDigits[n]}, ie = FromDigits[ Reverse[id]] - Union[id][[ -1]]; If[ie == 89, 0, ie]]; h[n_] := Length[NestWhileList[g, n, UnsameQ, All]] - 2; Do[ a = h[n]; If[a < 51 && t[[a]] == 0, t[[a]] = n], {n, 10^6}] (* _Robert G. Wilson v_, Aug 13 2004 *)

%Y Cf. A097153, A097154, A097155, A097157, A097158.

%K base,nonn

%O 1,2

%A _Jason Earls_, Aug 01 2004

%E More terms from _Robert G. Wilson v_, Aug 13 2004