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Numbers k such that 10^k + 13 is prime.
30

%I #27 Dec 15 2017 17:36:41

%S 1,2,3,17,25,81,140,142,152,280,291,406,4209,4785,8474,9550,9596,

%T 21773,22352,24938,38428,48526,65426,75441,76705

%N Numbers k such that 10^k + 13 is prime.

%C No other terms <= 100000. - _Robert Price_, Mar 03 2011

%t lst={};Do[If[PrimeQ[10^n+13], AppendTo[lst, n]], {n, 10^4}];lst [_Vladimir Joseph Stephan Orlovsky_, Aug 20 2008]

%o (PARI) for(n=1,1e4,if(ispseudoprime(10^n+13),print1(n", "))) \\ _Charles R Greathouse IV_, Jul 19 2011

%Y Cf. A095680 (the actual primes).

%K nonn,more

%O 1,2

%A _Jason Earls_, Jul 05 2004

%E More terms from _Ryan Propper_, Sep 07 2005

%E 5 more terms from _Jason Earls_, Feb 08 2008

%E a(23)=65426 from _Robert Price_, Jan 09 2011

%E a(24) and a(25) = 75441,76705 from _Robert Price_, Jan 29 2011