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A285938
Numbers k such that (19*10^k + 149)/3 is prime.
0
1, 2, 5, 7, 8, 11, 16, 29, 73, 169, 212, 227, 262, 547, 863, 1325, 2035, 4808, 8405, 13612, 16687, 19456, 122501
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 3 followed by the digits 83 is prime (see Example section).
a(24) > 2*10^5.
EXAMPLE
5 is in this sequence because (19*10^5+149)/3 = 633383 is prime.
Initial terms and associated primes:
a(1) = 1, 113;
a(2) = 2, 683;
a(3) = 5, 633383;
a(4) = 7, 63333383;
a(5) = 8, 633333383; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(19*10^# + 149)/3] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Apr 29 2017
EXTENSIONS
a(23) from Robert Price, May 17 2019
STATUS
approved