A232066 Periodic primes: primes p whose decimal expansion can be written as sss...st, where s is nonempty string of digits not beginning with 0, there are at least two copies of s, and t (which may be absent) is a prefix of s.

11, 18181, 32323, 35353, 72727, 74747, 78787, 94949, 95959, 1041041, 1051051, 1131131, 1191191, 1201201, 1212121, 1221221, 1231231, 1261261, 1281281, 1311311, 1381381, 1401401, 1411411, 1491491, 1501501, 1551551, 1581581, 1616161, 1621621, 1641641, 1671671

Offset: 1

Author

Paul Tek, Nov 17 2013

Keywords

• base
• nonn

Comments

The terms > 10^4 in A032758 appear in this sequence.

The terms > 10^20 in A231588 appear in this sequence.

Examples

			9779779 = 977|977|9,
727272727 = 72|72|72|72|7 = 7272|7272|7.
		

Links

• Paul Tek, Table of n, a(n) for n = 1..5972
• Paul Tek, PARI program for this sequence

Crossrefs

Cf. A032758, A231588.

A004022 is a subsequence (these are the terms where s=1 and t is absent). - Harvey P. Dale, Jul 09 2019

Programs

PARI

See Link section.

Extensions

Definition corrected by N. J. A. Sloane, Jul 09 2019