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A002235 Numbers n such that 3*2^n - 1 is prime.
(Formerly M0545 N0195)
26
0, 1, 2, 3, 4, 6, 7, 11, 18, 34, 38, 43, 55, 64, 76, 94, 103, 143, 206, 216, 306, 324, 391, 458, 470, 827, 1274, 3276, 4204, 5134, 7559, 12676, 14898, 18123, 18819, 25690, 26459, 41628, 51387, 71783, 80330, 85687, 88171, 97063, 123630, 155930, 164987, 234760, 414840, 584995, 702038, 727699, 992700, 1201046, 1232255, 2312734, 3136255, 4235414, 6090515, 11484018 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

REFERENCES

H. Riesel, Prime numbers and computer methods for factorization, Progress in Mathematics, Vol. 57, Birkhauser, 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).

LINKS

Table of n, a(n) for n=1..60.

C. K. Caldwell, The Prime Pages

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

Mersenne Forum, 321 Search

H. Riesel, Lucasian criteria for the primality of N=h.2^n-1, Math. Comp., 23 (1969), 869-875.

Eric Weisstein's World of Mathematics, Integer Sequence Primes

Eric Weisstein's World of Mathematics, Thabit ibn Kurrah Prime

Eric Weisstein's World of Mathematics, Thabit ibn Kurrah Rule

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

MATHEMATICA

lst={}; Do[If[PrimeQ[3*2^n-1], Print[n]; AppendTo[lst, n]], {n, 10^5}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 21 2008 *)

PROG

(PARI) is(n)=ispseudoprime(3<<n - 1) \\ Charles R Greathouse IV, Aug 27 2014

CROSSREFS

Cf. A000043, A007505, A003307, A046865, A079906, A046866, A001771, A005541, A056725, A046867, A079907.

Sequence in context: A074885 A215231 A091336 * A217132 A239014 A030705

Adjacent sequences:  A002232 A002233 A002234 * A002236 A002237 A002238

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Eric W. Weisstein, Sep 29 2007

Last term in The Prime Pages, from Pierre CAMI, Nov 25 2014

STATUS

approved

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Last modified December 20 07:03 EST 2014. Contains 252241 sequences.