A108334 - OEIS

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A108334

Numbers k such that the string 10197k is prime.

7, 13, 17, 23, 29, 31, 41, 47, 71, 83, 101, 107, 137, 157, 169, 193, 197, 217, 221, 223, 259, 301, 347, 373, 389, 391, 403, 427, 437, 469, 491, 497, 511, 527, 559, 563, 581, 587, 613, 631, 653, 673, 679, 683, 689, 701, 703, 727, 743, 749, 757, 799, 827, 833, 857, 893, 899, 907, 917

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

101 and 97 are primes.

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

EXAMPLE

k=7 and k=83 are in the sequence because 10197k = 101977 and 10197k = 1019783 are prime.

MATHEMATICA

Select[Range[10^3], PrimeQ[10197*10^IntegerLength[#] + #] &] (* Michael De Vlieger, Jan 22 2018 *)

PROG