A082705 Numbers k such that (29*10^(k-1) + 7)/9 is a depression prime.

7, 9, 895, 1525, 3037, 21157

Offset: 1

Author

Patrick De Geest, Apr 13 2003

Keywords

• nonn
• base
• hard
• more

Comments

Prime versus probable prime status and proofs are given in the author's table.

Examples

			k=9 -> (29*10^(9-1) + 7)/9 = 322222223.
		

References

• C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

Links

• Patrick De Geest, PDP Reference Table - 323.
• Makoto Kamada, Prime numbers of the form 322...223.
• Index entries for primes involving repunits.

Crossrefs

Cf. A082697-A082720, A056252.

Formula

a(n) = A056252(n) + 2.

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

Edited by Ray Chandler, Nov 05 2014