A193992 Position where 10^n-1 occurs in the Kaprekar sequence A006886.

2, 5, 8, 17, 24, 54, 62, 91, 102, 132, 149, 264, 281, 316, 385, 503, 527, 762, 790, 1035, 1154, 1278, 1378, 2304, 2374, 2498, 2575, 3122, 3910, 11330, 11714, 15400, 15478, 15642, 16039, 17892, 17909, 17968, 18401, 22238, 23747, 38524, 38728, 40625, 41101

Offset: 1

Author

T. D. Noe, Aug 17 2011

Keywords

• nonn
• base

Comments

Partial sums of A194232.

The Mathematica code computes 50 terms, but only these 45 terms are correct.

Links

• Hans Havermann, Table of n, a(n) for n = 1..196
• Index entries for Colombian or self numbers and related sequences

Crossrefs

Cf. A006886, A194232.

Programs

Mathematica

Inv[a_, b_] := PowerMod[a, -1, b]; t = {1}; Do[h = 10^k-1; d = Divisors[h]; d2 = Select[d, GCD[#, h/#] == 1 &]; AppendTo[t, h]; Do[AppendTo[t, d2[[i]]*Inv[d2[[i]], h/d2[[i]]]], {i, 2, Length[d2]-1}], {k, 50}]; t = Union[t]; Table[Position[t, 10^n-1, 1, 1][[1,1]], {n, Log[10, t[[-1]]]}]