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

2,1

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

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 *)

Crossrefs

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

Sequence in context: A196045 A196042 A177996 * A291473 A155769 A247390

Adjacent sequences: A217156 A217157 A217158 * A217160 A217161 A217162

Keyword

nonn,base

Author

V. Raman, Sep 27 2012

Status

approved