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URL: https://oeis.org/A295837

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A295837
Numbers k such that (37*10^k + 341)/9 is prime.
0
1, 2, 4, 7, 10, 11, 17, 20, 65, 70, 811, 947, 1099, 1487, 1540, 6617, 15067, 18433, 19063, 31462, 131270
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 1 followed by the digits 49 is prime (see Example section).
a(22) > 2*10^5.
EXAMPLE
2 is in this sequence because (37*10^2 + 341)/9 = 449 is prime.
Initial terms and associated primes:
a(1) = 1, 79;
a(2) = 2, 449;
a(3) = 4, 41149;
a(4) = 7, 41111149;
a(5) = 10, 41111111149; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(37*10^# + 341)/9] &]
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 28 2017
EXTENSIONS
a(21) from Robert Price, Aug 14 2018
STATUS
approved