A082712 Numbers k such that (67*10^(k-1) + 23)/9 is a depression prime.

11, 31, 121, 485, 1487, 1579, 13673, 13811, 15095, 72773, 94212

Offset

1,1

Comments

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

References

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

Links

Table of n, a(n) for n=1..11.

Patrick De Geest, PDP Reference Table - 747.

Makoto Kamada, Prime numbers of the form 744...447.

Index entries for primes involving repunits.

Formula

a(n) = A056258(n) + 2.

Example

k=11 -> (67*10^(11-1) + 23)/9 = 74444444447.

Crossrefs

Cf. A082697-A082720, A056258.

Sequence in context: A223388 A152220 A272263 * A049090 A181150 A094622

Adjacent sequences: A082709 A082710 A082711 * A082713 A082714 A082715

Keyword

nonn,base,hard,more

Author

Patrick De Geest, Apr 13 2003

Extensions

a(10)=72773 from Ray Chandler, Nov 16 2010

a(11)=94212 from Ray Chandler, Feb 21 2011

Edited by Ray Chandler, Nov 05 2014

Status

approved