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Integers k such that 10^k+49 is prime.
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%I #40 Jul 10 2023 09:53:20

%S 1,2,3,5,8,17,24,32,65,66,67,79,83,98,152,260,781,1225,1777,2023,2411,

%T 3469,5347,10646,11335,13989,14792,16731,19015,29471,39187,41456,

%U 80883,102824,154359,216950,294475

%N Integers k such that 10^k+49 is prime.

%C See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "10049".

%C a(38) > 3*10^5. _Robert Price_, Jul 10 2023

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/">List of near-repdigit-related prime numbers</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.

%e k = 8 ==> 10^8+49 = 100000049, which is prime.

%t a={};Do[p=10^n+49;If[PrimeQ[p],AppendTo[a,n]],{n,0,10^3,1}];a (* _Vladimir Joseph Stephan Orlovsky_, Jul 17 2008 *)

%o (PARI) for(n=1,1e4,if(ispseudoprime(10^n+49),print1(n", "))) \\ _Charles R Greathouse IV_, Jul 25 2011

%Y Cf. A049054, A088274, A088275, A095688.

%K nonn,more

%O 1,2

%A Julien Peter Benney (jpbenney(AT)ftml.net), Jun 02 2005

%E a(23) from _Ray G. Opao_, Dec 13 2006

%E a(24)-a(31) from _Robert Price_, May 28 2010

%E Edited by _Ray Chandler_, Dec 23 2010

%E a(32) from _Robert Price_, Dec 27 2010

%E a(33) from _Robert Price_, Mar 03 2011

%E a(34)-a(37) from _Robert Price_, Jul 10 2023