A172459 Primes p such that exactly one of the numbers 2p-1 and 2^p - 1 is prime.

5, 13, 17, 37, 61, 79, 89, 97, 107, 127, 139, 157, 199, 211, 229, 271, 307, 331, 337, 367, 379, 439, 499, 521, 547, 577, 601, 619, 661, 691, 727, 811, 829, 877, 937, 967, 997, 1009, 1069, 1171, 1237, 1297, 1399, 1429, 1459, 1531, 1609, 1627, 1657, 1759, 1867

Offset

1,1

Links

Table of n, a(n) for n=1..51.

Example

a(1)=5=prime because 2^5-1=31=prime and 2*5-1=9=nonprime; a(2)=13=prime because 2^13-1=8191=prime and 2*13-1=25=nonprime.

Crossrefs

Cf. A000043, A000668, A005382.

Sequence in context: A189411 A248980 A188131 * A084165 A120130 A087484

Adjacent sequences: A172456 A172457 A172458 * A172460 A172461 A172462

Keyword

nonn

Author

Juri-Stepan Gerasimov, Feb 03 2010, Feb 06 2010

Extensions

Corrected by Juri-Stepan Gerasimov, Feb 06 2010

Definition edited by Emeric Deutsch, Feb 13 2010

Extended by Emeric Deutsch, Feb 13 2010

Status

approved