A242387 Lesser of consecutive primes whose average is a palindromic number.

3, 5, 7, 97, 109, 281, 359, 389, 409, 509, 631, 653, 691, 743, 827, 857, 907, 937, 967, 1549, 2111, 2767, 4219, 4441, 7001, 9007, 9337, 9661, 10099, 11503, 12919, 13421, 16759, 17569, 21011, 21611, 23831, 26261, 26861, 28181, 29287, 29483, 30497, 31307, 32213, 33029, 33629

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

389 is in the sequence because 389 is prime, nextprime(389)=397, and (389+397)/2=393, a palindromic number.

Mathematica

Select[Partition[Prime[Range[4000]], 2, 1], PalindromeQ[Mean[#]]&][[All, 1]] (* Requires Mathematica version 10 or later *)  (* Harvey P. Dale, Apr 05 2019 *)

Prog

(PARI)
palind(n)=Str(n)==concat(Vecrev(Str(n)))
{p=2; while(p<10^5, q=nextprime(p+1); if(palind((p+q)/2), print1(p, ", ")); p=q)}

Crossrefs

Cf. A242386.

Sequence in context: A160360 A082697 A051345 * A104388 A110337 A132287

Adjacent sequences: A242384 A242385 A242386 * A242388 A242389 A242390

Keyword

nonn,base,less

Author

Antonio Roldán, May 12 2014

Status

approved