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A217159 a(n) is the least value of k such that the decimal expansion of n^k contains four consecutive identical digits. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

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,changed

AUTHOR

V. Raman, Sep 27 2012

STATUS

approved

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Last modified July 1 22:23 EDT 2022. Contains 354984 sequences. (Running on oeis4.)