

A228627


Primes of the form abcabc..abcab.


4



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
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OFFSET

1,1


COMMENTS

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


LINKS



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



KEYWORD

nonn,base


AUTHOR



STATUS

approved



