A082622 - OEIS

A082622

a(1) = 3, a(n) = smallest palindromic prime obtained by inserting two paired digits anywhere in a(n-1).

%I #57 Dec 05 2024 15:30:25

%S 3,131,10301,1003001,100030001,10070307001,1000703070001,

%T 100075030570001,10006750305760001,1000167503057610001,

%U 100015675030576510001,10001056750305765010001,1000105367503057635010001,100001053675030576350100001,10000105360750305706350100001

%N a(1) = 3, a(n) = smallest palindromic prime obtained by inserting two paired digits anywhere in a(n-1).

%C With the exception of 11, all decimal palindromic numbers with an even number of digits are composite (they are divisible by 11). This leaves only odd-digit-length palindromes, therefore (at least) a pair of digits needs to be inserted at every iteration.

%C The sequence terminates at a(19) = 1000010025136075033305706315200100001, which cannot be extended to another palindromic prime by inserting two paired digits. - _Giovanni Resta_, Sep 20 2019

%H Giovanni Resta, <a href="/A082622/b082622.txt">Table of n, a(n) for n = 1..19</a>

%Y Cf. A082620, A082621.

%K nonn,base,fini,full

%O 1,1

%A _Amarnath Murthy_, Apr 29 2003

%E Terms following a(6) corrected by _Giovanni Resta_, Sep 20 2019

%E Deleted an incorrect program. - _N. J. A. Sloane_, Dec 05 2024