A206430 Least k such that k*2^m - 1 has a covering set with precisely n primes.

509203, 777149, 7106977, 60014203

Offset

6,1

Comments

A set of primes is a covering set for k*2^m - 1 if for every positive integer m there is some prime in the set which divides k*2^m - 1. Only minimal covering sets are considered here (those which would not remain covering sets with the removal of any element).

Links

Table of n, a(n) for n=6..9.

Wikipedia, Covering set

Wikipedia, Riesel number

Example

509203 has the covering set {3, 5, 7, 13, 17, 241}.
777149 has the covering set {3, 5, 7, 13, 19, 37, 73}.
7106977 has the covering set {3, 5, 13, 17, 19, 109, 241, 433}.
60014203 has the covering set {3, 5, 7, 11, 13, 31, 41, 61, 151}.

Crossrefs

Cf. A076337, A101036.

Sequence in context: A258154 A101036 A244070 * A182296 A263958 A273987

Adjacent sequences: A206427 A206428 A206429 * A206431 A206432 A206433

Keyword

more,nonn

Author

Arkadiusz Wesolowski, Apr 19 2012

Status

approved