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A001775 Numbers k such that 19*2^k - 1 is prime.
(Formerly M2506 N0991)
5
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 (list; graph; refs; listen; history; text; internal format)
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
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.
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
KEYWORD
nonn,hard,more
AUTHOR
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

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Last modified March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)