A217159 a(n) is the least value of k such that the decimal expansion of n^k contains four consecutive identical digits.

41, 33, 90, 95, 115, 71, 60, 88, 4, 39, 18, 25, 14, 98, 45, 52, 78, 70, 4, 29, 42, 35, 41, 48, 44, 11, 21, 37, 4, 18, 36, 71, 34, 18, 64, 20, 39, 32, 4, 40, 20, 20, 45, 33, 33, 14, 36, 40, 4, 37, 42, 29, 39, 63, 24, 10, 26, 10, 4, 64, 15, 30, 30, 18, 17, 58

Offset: 2

Author

V. Raman, Sep 27 2012

Keywords

• nonn
• base

Comments

The term 76 appears for the first time in this sequence at n = 112044721958. - Paul Geneau de Lamarlière, Jun 25 2024

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]], 3, 1], {0, 0, 0}], k++]; k, {n, 2, 100}] (* T. D. Noe, Oct 01 2012 *)
lk[n_]:=Module[{k=1,t=Table[x_,4]},While[SequenceCount[IntegerDigits[n^k],t]< 1,k++];k];Array[lk,80,2] (* Harvey P. Dale, Jun 21 2022 *)