The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

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