A108111 Numbers k such that the string 2931k is prime.

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

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