

A002235


Numbers n such that 3*2^n  1 is prime.
(Formerly M0545 N0195)


25



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
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OFFSET

1,3


REFERENCES

H. Riesel, Lucasian criteria for the primality of N=h.2^n1, Math. Comp., 23 (1969), 869875.
H. Riesel, ``Prime numbers and computer methods for factorization,'' Progress in Mathematics, Vol. 57, Birkhauser, Boston, 1985, Chap. 4, see pp. 381384.
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..59.
C. K. Caldwell, The Prime Pages
Wilfrid Keller, List of primes k.2^n  1 for k < 300
Mersenne Forum, 321 Search
Eric Weisstein's World of Mathematics, Integer Sequence Primes
Eric Weisstein's World of Mathematics, Thabit ibn Kurrah Number
Eric Weisstein's World of Mathematics, Thabit ibn Kurrah Rule
Index entries for sequences of n such that k*2^n1 (or k*2^n+1) is prime


MATHEMATICA

lst={}; Do[If[PrimeQ[3*2^n1], Print[n]; AppendTo[lst, n]], {n, 10^5}]; lst [From 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


STATUS

approved



