A217158 a(n) is the least value of k such that the decimal expansion of n^k contains three consecutive identical digits.

24, 32, 12, 50, 5, 31, 8, 16, 3, 8, 17, 25, 14, 23, 6, 12, 6, 9, 3, 11, 7, 15, 14, 25, 11, 11, 10, 5, 3, 7, 8, 10, 10, 18, 9, 15, 2, 12, 3, 14, 4, 7, 12, 18, 12, 8, 17, 17, 3, 15, 10, 7, 11, 25, 24, 8, 11, 10, 3, 14, 11, 18, 4, 7, 9, 13, 7, 12, 3, 11, 8, 13

Offset: 2

Author

V. Raman, Sep 27 2012

Keywords

• nonn
• base

Links

• V. Raman, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A045875, A215727, A215728, A215729, A215730, A215731.

Programs

Mathematica

Table[k = 1; While[! MemberQ[Partition[Differences[IntegerDigits[n^k]], 2, 1], {0, 0}], k++]; k, {n, 2, 100}] (* T. D. Noe, Oct 01 2012 *)
lvk[n_]:=Module[{k=1},While[SequenceCount[IntegerDigits[n^k],{x_,x_,x_}]<1,k++];k]; Array[lvk,80,2] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Mar 13 2018 *)