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A108102 Numbers k such that the string 1117k is prime. 0
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 (list; graph; refs; listen; history; text; internal format)
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 * A065523 A046528 A018572

Adjacent sequences:  A108099 A108100 A108101 * A108103 A108104 A108105

KEYWORD

nonn,base

AUTHOR

Parthasarathy Nambi, Jun 25 2005

STATUS

approved

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Last modified February 17 18:14 EST 2020. Contains 332005 sequences. (Running on oeis4.)