A001775 Numbers k such that 19*2^k - 1 is prime. (Formerly M2506 N0991)

1, 3, 5, 21, 41, 49, 89, 133, 141, 165, 189, 293, 305, 395, 651, 665, 771, 801, 923, 953, 3689, 5315, 6989, 15641, 48819, 78389, 134053, 167843, 181395, 311091, 353661, 645555, 916763

Offset

1,2

References

H. Riesel, "Prime numbers and computer methods for factorization", Progress in Mathematics, Vol. 57, Birkhäuser, Boston, 1985, Chap. 4, see pp. 381-384.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

H. C. Williams and C. R. Zarnke, Math. Comp., 22 (1968), 420-422.

Links

Table of n, a(n) for n=1..33.

Wilfrid Keller, List of primes k.2^n - 1 for k < 300

Kosmaj, Riesel list k<300.

H. C. Williams and C. R. Zarnke, A report on prime numbers of the forms M = (6a+1)*2^(2m-1)-1 and (6a-1)*2^(2m)-1, Math. Comp., 22 (1968), 420-422.

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Prog

(PARI) is(n)=ispseudoprime(19*2^n-1) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A032359 (19*2^k+1 is prime).

Sequence in context: A288152 A082699 A096729 * A148548 A148549 A148550

Adjacent sequences: A001772 A001773 A001774 * A001776 A001777 A001778

Keyword

nonn,hard,more

Author

N. J. A. Sloane

Extensions

More terms from Hugo Pfoertner, Jun 22 2004

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

Minor corrections by Charles R Greathouse IV, Aug 29 2010

Status

approved