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A089319 Smallest k > 1 such that k^n followed by digit 1 is a prime. 1
3, 2, 3, 3, 6, 2, 3, 6, 3, 11, 7, 2, 70, 2, 22, 18, 43, 3, 4, 649, 15, 3, 37, 2, 24, 13, 4, 8, 40, 77, 19, 22, 13, 24, 292, 48, 4, 2, 109, 792, 30, 4, 18, 5, 7, 90, 28, 138, 132, 891, 9, 25, 145, 2, 24, 9, 40, 28, 219, 165, 40, 41, 4, 13, 261, 24, 6, 30, 6, 154, 82, 22, 120, 2, 55 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..75.

EXAMPLE

a(4) = 3 as concatenation of 3^4 and 1 = 811 is a prime. 161 is not a prime.

MATHEMATICA

Do[k = 2; While[ !PrimeQ[10*k^n + 1], k++ ]; Print[k], {n, 1, 30}] (* Ryan Propper, Jul 08 2005 *)

CROSSREFS

Cf. A089318.

Sequence in context: A058680 A070544 A087713 * A140396 A117231 A106151

Adjacent sequences:  A089316 A089317 A089318 * A089320 A089321 A089322

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 03 2003

EXTENSIONS

Corrected and extended by Ryan Propper, Jul 08 2005

Further terms from David Wasserman, Sep 09 2005

STATUS

approved

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Last modified May 14 16:48 EDT 2021. Contains 343898 sequences. (Running on oeis4.)