A001775 Numbers k such that 19*2^k - 1 is prime.

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

Author

N. J. A. Sloane

Keywords

• nonn
• hard
• more

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

• 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

Crossrefs

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

Programs

PARI

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

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