A228627 Primes of the form abcabc..abcab.

11311, 11411, 13313, 13513, 13613, 13913, 17117, 17317, 17417, 19219, 19319, 19819, 19919, 21121, 21221, 21521, 21821, 23623, 27127, 27427, 27527, 27827, 29129, 29429, 29629, 31231, 31531, 33533, 37337, 37537, 39139, 39239, 39439, 39839, 41141, 41341, 41641

Offset

1,1

Comments

The sequence appears to be infinite. The number of terms below 10^1000 is 782.

Links

Shyam Sunder Gupta, Table of n, a(n) for n = 1..500

Example

a(2)= 11411 is in the sequence because it is a prime of the form abcab.

Mathematica

s[n_]:=Select[Union@Flatten@Table[FromDigits@Flatten@Join[IntegerDigits@Table[b, {n}], {IntegerDigits@Floor[b/10]}], {b, 100, 999}], PrimeQ]; Array[s, 2]//Flatten
Select[FromDigits[Join[#, {#[[1]]}, {#[[2]]}]]&/@Select[Tuples[Range[0, 9], 3], #[[1]]> 0&], PrimeQ] (* Harvey P. Dale, Oct 06 2017 *)

Crossrefs

Sequence in context: A104017 A317400 A284814 * A178581 A178583 A178589

Adjacent sequences: A228624 A228625 A228626 * A228628 A228629 A228630

Keyword

nonn,base

Author

Shyam Sunder Gupta, Aug 28 2013

Status

approved