A082714 Numbers n such that 2*(10^n-1)/3+(10^(n-1)+1) or (69*10^(n-1)+3)/9 is a plateau or depression prime.

5, 7, 55, 97, 455, 575, 3385, 11441, 12625, 19447, 35461, 81215, 95327

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..13.

Patrick De Geest, PDP Reference Table - 767.

Makoto Kamada, Prime numbers of the form 766...667.

Index entries for primes involving repunits.

Example

7 is a term because 2*(10^7-1)/3+(10^6+1) = 7666667.

Crossrefs

Cf. A082697-A082720, A056260.

Sequence in context: A320108 A320112 A284380 * A300090 A324984 A106112

Adjacent sequences: A082711 A082712 A082713 * A082715 A082716 A082717

Keyword

nonn,base,more

Author

Patrick De Geest, Apr 13 2003

Extensions

35461 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

Added two more terms from PDP table, by Patrick De Geest, Nov 04 2014

Edited by Ray Chandler, Nov 05 2014

Name clarified by Michel Marcus, Mar 27 2020

Status

approved