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A295401
Numbers k such that 3*10^k + 97 is prime.
0
1, 2, 4, 14, 19, 22, 87, 141, 228, 274, 441, 514, 721, 1674, 1710, 2725, 2858, 4658, 19862, 20175, 25474, 30309, 34740
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 97 is prime (see Example section).
a(24) > 2*10^5.
EXAMPLE
2 is in this sequence because 3*10^2 + 97 = 397 is prime.
Initial terms and associated primes:
a(1) = 1, 127;
a(2) = 2, 397;
a(3) = 4, 30097;
a(4) = 14, 300000000000097;
a(5) = 19, 30000000000000000097; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[3*10^# + 97] &]
PROG
(PARI) isok(k) = isprime(3*10^k + 97); \\ Michel Marcus, Nov 22 2017
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 21 2017
STATUS
approved