A107083 Integers k such that 10^k + 31 is prime.

1, 2, 3, 14, 18, 44, 54, 89, 469, 2060, 2985, 6197, 16452, 19393, 21205, 49657, 74670, 76374

Offset: 1

Author

Julien Peter Benney (jpbenney(AT)ftml.net), Jun 08 2005

Keywords

• more
• nonn

Comments

The next term, if one exists, is >100000. - Robert Price, Apr 26 2011

See Kamada link - primecount.txt for terms, primesize.txt for discovery details including proofs of primality - search on "10031".

Examples

			For k = 3 we get 10^3 + 31 = 1000 + 31 = 1031, 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, A108052, A108050, A108049, A108054.

Programs

Mathematica

a={}; Do[If[PrimeQ[p=10^n+31], AppendTo[a, n]], {n, 0, 6*10^2}]; a (* Vladimir Joseph Stephan Orlovsky, Aug 07 2008 *)

Extensions

16452 and 19393 from Robert Price, Mar 22 2010

Additional term (21205) from Robert Price, May 24 2010

Missing term (6197) added by Robert Price, Dec 07 2010

Edited by Ray Chandler, Dec 23 2010

a(16)=49657 from Robert Price, Dec 31 2010

a(17)=74670 from Robert Price, Jan 29 2011

a(18)=76374 from Robert Price, Mar 03 2011