A102503 Primes of the concatenated form 9nn9.

910109, 913139, 916169, 917179, 920209, 923239, 928289, 931319, 935359, 937379, 946469, 953539, 956569, 961619, 965659, 968689, 974749, 982829, 994949, 995959, 998989, 9101010109, 9101310139, 9101810189, 9104210429, 9104810489

Offset: 1

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005

Keywords

• easy
• nonn
• base

Examples

			910109 is prime and of the form 9nn9 for n=10.
9101310139 is prime and of the form 9nn9 for n=1013.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..2500

Crossrefs

Cf. A102484 for sequence of all numbers of form 9nn9. A102502 for the n values corresponding to the primes in this sequence.

Programs

Mathematica

Select[Table[FromDigits[Join[{9},IntegerDigits[n],IntegerDigits[n],{9}]],{n,1100}],PrimeQ] (* Harvey P. Dale, Jul 28 2020 *)