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A242387 Lesser of consecutive primes whose average is a palindromic number. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 1 15:59 EST 2022. Contains 358468 sequences. (Running on oeis4.)