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A271505
Numbers k such that (82*10^k + 161)/9 is prime.
0
1, 2, 4, 5, 7, 8, 14, 17, 22, 49, 130, 136, 142, 170, 196, 220, 967, 1816, 2165, 2542, 2635, 3979, 10319, 11096, 12191, 14381, 14444, 17558, 18230, 42176, 113681
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 1 followed by the digits 29 is prime (see Example section).
a(32) > 2*10^5.
EXAMPLE
4 is in this sequence because (82*10^4+161)/9 = 91129 is prime.
Initial terms and associated primes:
a(1) = 1, 109;
a(2) = 2, 929;
a(3) = 4, 91129;
a(4) = 5, 911129;
a(5) = 7, 91111129, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(82*10^# + 161)/9] &]
PROG
(PARI) is(n)=ispseudoprime((82*10^n + 161)/9) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,more
AUTHOR
Robert Price, Apr 08 2016
EXTENSIONS
a(31) from Robert Price, Oct 31 2019
STATUS
approved