A108102 Numbers k such that the string 1117k is prime.

1, 3, 7, 21, 31, 33, 51, 67, 73, 79, 81, 91, 99, 111, 117, 153, 169, 177, 199, 243, 247, 253, 267, 273, 279, 301, 307, 309, 321, 349, 367, 379, 433, 439, 451, 463, 471, 477, 481, 483, 489, 513, 549, 553, 579, 591, 601, 603, 607, 609, 657, 661, 673, 679, 681

Offset

1,2

Comments

Leading zeros in k are not permitted; cases like k=013 relating to the prime 1117013 are not in the sequence.

Links

Table of n, a(n) for n=1..55.

Example

k=1 and k=79 are in the sequence because 1117k = 11171 and 1117k=111779 are prime.

Mathematica

Select[Range[700], PrimeQ[FromDigits[Join[{1, 1, 1, 7}, IntegerDigits[ #]]]]&] (* Harvey P. Dale, Sep 13 2011 *)

Prog

(Magma) [ n: n in [1..700] | IsPrime(Seqint(Intseq(n) cat [7, 1, 1, 1])) ]; // Vincenzo Librandi, Feb 02 2011

Crossrefs

Cf. A107645, A107644.

Sequence in context: A018548 A323585 A003585 * A357898 A065523 A046528

Adjacent sequences: A108099 A108100 A108101 * A108103 A108104 A108105

Keyword

nonn,base

Author

Parthasarathy Nambi, Jun 25 2005

Status

approved