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A174175
Numbers n such that 10^n + 2*n - 1 is prime.
2
1, 2, 4, 10, 20, 35, 91, 112, 116, 325, 367, 674, 2440, 14099, 38315, 47989
OFFSET
1,2
COMMENTS
a(17) > 10^5. - Robert Price, Mar 24 2015
MATHEMATICA
Select[Range[5000], PrimeQ[(10^# + 2 # - 1)] &] (* Vincenzo Librandi, Oct 05 2012 *)
PROG
(Magma) /* The code gives only the terms up to 367: */ [n: n in [1..500] | IsPrime(10^n+2*n-1)];
(PARI) is(n)=ispseudoprime(10^n+2*n-1) \\ Charles R Greathouse IV, Jun 06 2017
CROSSREFS
Cf. A173851 (accociated primes).
Sequence in context: A271624 A283090 A283143 * A127392 A236001 A258092
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Mar 11 2010
EXTENSIONS
a(11)-a(13) from Vincenzo Librandi, Oct 05 2012
a(14)-a(16) from Robert Price, Mar 24 2015
STATUS
approved