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

1,2

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

Links

Table of n, a(n) for n=1..37.

Makoto Kamada, List of near-repdigit-related prime numbers.

Index entries for primes involving repunits.

Example

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

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 *)

Prog

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

Crossrefs

Cf. A049054, A088274, A088275, A095688.

Sequence in context: A308852 A093000 A122630 * A342690 A123612 A077177

Adjacent sequences: A108051 A108052 A108053 * A108055 A108056 A108057

Keyword

nonn,more

Author

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

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

Status

approved