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A002253 Numbers n such that 3*2^n+1 is prime.
(Formerly M1318 N0506)
6
1, 2, 5, 6, 8, 12, 18, 30, 36, 41, 66, 189, 201, 209, 276, 353, 408, 438, 534, 2208, 2816, 3168, 3189, 3912, 20909, 34350, 42294, 42665, 44685, 48150, 54792, 55182, 59973, 80190, 157169, 213321, 303093, 362765, 382449, 709968, 801978, 916773, 1832496, 2145353, 2291610, 2478785, 5082306, 7033641, 10829346 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From Zak Seidov, Mar 08 2009: (Start)

List is complete up to 3941000 according to the list of RB & WK.

So far there are only 4 primes: 2, 5, 41, 353. (End)

REFERENCES

D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, Vol. 2, p. 614.

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..49.

Ray Ballinger, Proth Search Page

Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300

C. K. Caldwell, The Prime Pages

Y. Gallot, Proth.exe: Windows Program for Finding Large Primes

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

Eric Weisstein's World of Mathematics, Proth Prime

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

CROSSREFS

Cf. A039687, A002254.

Sequence in context: A230902 A243680 A105107 * A032716 A132229 A028750

Adjacent sequences:  A002250 A002251 A002252 * A002254 A002255 A002256

KEYWORD

hard,nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

Corrected and extended according to the list of Ray Ballinger and Wilfrid Keller by Zak Seidov, Mar 08 2009

Edited by N. J. A. Sloane, Mar 13 2009

Two more terms (from http://www.prothsearch.net/riesel.html), Joerg Arndt, Apr 07 2013

One more term (from http://primes.utm.edu/primes/page.php?id=116922), Fabrice Le Foulher, Mar 09 2014

STATUS

approved

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Last modified October 31 08:19 EDT 2014. Contains 248850 sequences.