A109355 - OEIS

A109355

Numbers k such that the string 23572357k is prime.

7, 19, 31, 37, 43, 57, 61, 103, 169, 213, 229, 243, 273, 337, 339, 349, 357, 387, 421, 441, 453, 463, 469, 483, 531, 541, 559, 577, 583, 597, 621, 631, 637, 643, 681, 687, 729, 759, 789, 819, 877, 901, 927, 931, 937, 1011, 1033, 1047, 1051, 1071, 1077, 1093, 1101, 1141, 1143, 1201

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

OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

k=7 is in the sequence because 23572357k = 235723577 is prime.

k=213 is in the sequence because 23572357k = 23572357213 is prime.

MAPLE

q:= 23572357:

select(n -> isprime(q*10^(1+ilog10(n))+n), [seq(i, i=1..10000, 2)]); # Robert Israel, Jan 22 2018

MATHEMATICA