A100028 Values of n for which the decimal number 10...030...01 is an n-digit prime.

3, 5, 7, 9, 23, 29, 33, 185, 267, 307, 757, 897, 1571, 2977, 3831, 4595, 6573, 9511, 11651, 15641, 68885, 69883

Offset: 1

Author

Harvey Dubner (harvey(AT)dubner.com), Nov 20 2004

Keywords

• nonn
• base
• more

Examples

			The corresponding primes are 131, 10301, 1003001, 100030001, 10000000000300000000001, etc.
		

Crossrefs

Cf. A100026, A100027, A100456, A100457, A100458, A100459.

Programs

Mathematica

IntegerLength/@Select[Table[FromDigits[Join[PadRight[{1},n,0],{3},PadLeft[ {1},n,0]]],{n,35000}],PrimeQ] (* Harvey P. Dale, Dec 20 2019 *)

Formula

a(n) = 2*(A171376(n+1))+1. - Chai Wah Wu, Aug 20 2015