A082622 a(1) = 3, a(n) = smallest palindromic prime obtained by inserting two paired digits anywhere in a(n-1).

3, 131, 10301, 1003001, 100030001, 10070307001, 1000703070001, 100075030570001, 10006750305760001, 1000167503057610001, 100015675030576510001, 10001056750305765010001, 1000105367503057635010001, 100001053675030576350100001, 10000105360750305706350100001

Offset: 1

Author

Amarnath Murthy, Apr 29 2003

Keywords

• nonn
• base
• fini
• full

Comments

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.

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

Links

• Giovanni Resta, Table of n, a(n) for n = 1..19

Crossrefs

Cf. A082620, A082621.

Extensions

Terms following a(6) corrected by Giovanni Resta, Sep 20 2019

Deleted an incorrect program. - N. J. A. Sloane, Dec 05 2024