A108054 Integers k such that 10^k+49 is prime.

1, 2, 3, 5, 8, 17, 24, 32, 65, 66, 67, 79, 83, 98, 152, 260, 781, 1225, 1777, 2023, 2411, 3469, 5347, 10646, 11335, 13989, 14792, 16731, 19015, 29471, 39187, 41456, 80883, 102824, 154359, 216950, 294475

Offset: 1

Author

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

Keywords

• nonn
• more

Comments

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

a(38) > 3*10^5. Robert Price, Jul 10 2023

Examples

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

Links

• Makoto Kamada, List of near-repdigit-related prime numbers.
• Index entries for primes involving repunits.

Crossrefs

Cf. A049054, A088274, A088275, A095688.

Programs

Mathematica

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 *)

PARI

for(n=1,1e4,if(ispseudoprime(10^n+49),print1(n", "))) \\ Charles R Greathouse IV, Jul 25 2011

Extensions

a(23) from Ray G. Opao, Dec 13 2006

a(24)-a(31) from Robert Price, May 28 2010

Edited by Ray Chandler, Dec 23 2010

a(32) from Robert Price, Dec 27 2010

a(33) from Robert Price, Mar 03 2011

a(34)-a(37) from Robert Price, Jul 10 2023