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A295328
Numbers k such that 3*10^k + 67 is prime.
0
1, 2, 3, 25, 61, 75, 99, 122, 145, 187, 292, 586, 1328, 2457, 3410, 4819, 5986, 6638, 20855, 28161, 47647, 49387, 67499, 72723
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 67 is prime (see Example section).
a(25) > 2*10^5.
EXAMPLE
2 is in this sequence because 3*10^2 + 67 = 367 is prime.
Initial terms and associated primes:
a(1) = 1, 97;
a(2) = 2, 367;
a(3) = 3, 3067;
a(4) = 25, 30000000000000000000000067; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[3*10^# + 67] &]
PROG
(PARI) isok(k) = isprime(3*10^k + 67); \\ Michel Marcus, Nov 20 2017
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 19 2017
STATUS
approved