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URL: https://oeis.org/A288150

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A288150
Numbers k such that (25*10^k + 23)/3 is prime.
0
4, 8, 11, 12, 16, 20, 22, 34, 35, 38, 51, 52, 106, 135, 168, 189, 194, 224, 482, 3456, 4832, 36022, 52119
OFFSET
1,1
COMMENTS
For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 3 followed by the digits 41 is prime (see Example section).
a(24) > 2*10^5.
EXAMPLE
4 is in this sequence because (25*10^4 + 23)/3 = 83341 is prime.
Initial terms and associated primes:
a(1) = 4, 83341;
a(2) = 8, 833333341;
a(3) = 11, 833333333341;
a(4) = 12, 8333333333341;
a(5) = 16, 83333333333333341; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(25*10^# + 23)/3] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jun 05 2017
STATUS
approved