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A108111 Numbers k such that the string 2931k is prime. 0
1, 23, 29, 47, 49, 73, 77, 79, 101, 113, 127, 151, 161, 167, 193, 197, 209, 211, 217, 221, 223, 241, 289, 307, 319, 413, 421, 427, 433, 443, 457, 493, 503, 527, 553, 569, 583, 587, 619, 629, 637, 647, 653, 671, 683, 707, 713, 739 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..48.

EXAMPLE

k=1 is in the sequence because 2931k = 29311 is a prime number.

k=113 is in the sequence because 2931k = 2931113 is a prime number.

MATHEMATICA

Select[Range[1000], PrimeQ[#+2931 10^IntegerLength[#]]&] (* Harvey P. Dale, Sep 16 2011 *)

PROG

(MAGMA) [ n: n in [1..750] | IsPrime(Seqint(Intseq(n) cat [1, 3, 9, 2])) ]; // Vincenzo Librandi, Feb 02 2011

CROSSREFS

Sequence in context: A106989 A106988 A127834 * A085713 A102904 A108249

Adjacent sequences:  A108108 A108109 A108110 * A108112 A108113 A108114

KEYWORD

nonn,base

AUTHOR

Parthasarathy Nambi, Jun 25 2005

STATUS

approved

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Last modified October 18 13:31 EDT 2019. Contains 328161 sequences. (Running on oeis4.)