A030464 Primes that are the concatenation of two consecutive palindromic primes.

23, 3151332323, 3242333533, 3727337573, 3757338083, 7888779397, 11202111123211, 11232111126211, 11606111163611, 11787111180811, 12626211268621, 12737211276721, 13111311317131, 13353311338331

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

digrev:= proc(n) local L, i;
  L:= convert(n, base, 10);
  add(L[-i]*10^(i-1), i=1..nops(L))
end proc:
dcat:= proc(x, y) 10^(1+ilog10(y))*x+y end proc:
R:= 23: count:= 1: lastpp:= 3:
for d from 2 while count < 100 do
  for i in [1, 3, 7, 9] while count < 100 do
    for m from i*10^(d-1)+1 to (i+1)*10^(d-1)-1 while count < 100 do
      for j from 0 to 9 while count < 100 do
    x:= m*10^(d+1)+j*10^d+digrev(m);
    if isprime(x) then
       y:= dcat(lastpp, x);
       lastpp:= x;
       if isprime(y) then R:= R, y; count:= count+1 fi
    fi
od od od od:
R; # Robert Israel, Apr 01 2021

Mathematica

Select[FromDigits[Flatten[IntegerDigits/@#]]&/@Partition[Select[Prime[Range[ 110000]], PalindromeQ], 2, 1], PrimeQ] (* Harvey P. Dale, Mar 31 2023 *)

Crossrefs

Cf. A002385.

Sequence in context: A087527 A013906 A214360 * A180731 A053558 A140793

Adjacent sequences: A030461 A030462 A030463 * A030465 A030466 A030467

Keyword

nonn,base

Author

Patrick De Geest

Extensions

Edited by Charles R Greathouse IV, Apr 28 2010

Status

approved