A159031 Primes of the form "1 [0]_n 7" - with zeros between 1 and 7.

17, 107, 10007, 100000007, 1000000007, 1000000000000000000000007, 1000000000000000000000000000000000000000000000000000000000007

Offset: 1

Author

Parthasarathy Nambi, Apr 02 2009

Keywords

• nonn
• base

Comments

The next term, a(8), has 111 digits. - Harvey P. Dale, Nov 12 2011

Examples

			1000000000000000000000007 is a prime with 23 zeros between 1 and 7.
		

Links

• Dario Alejandro Alpern, Factorization using the Elliptic Curve Method.
• Makoto Kamada, Prime numbers of the form 100...007.
• Index entries for primes involving repunits.

Crossrefs

Cf. A088274. - Robert G. Wilson v, Apr 05 2009

Programs

Mathematica

Do[ If[ PrimeQ[10^n + 7], Print[10^n + 7]], {n, 100}] (* Robert G. Wilson v, Apr 05 2009 *)
Select[Table[FromDigits[Join[{1},PadRight[{},n,0],{7}]],{n,0,120}],PrimeQ] (* Harvey P. Dale, Nov 12 2011 *)

Extensions

a(7) from Robert G. Wilson v, Apr 05 2009