

A005540


Numbers k such that 4*3^k  1 is prime.
(Formerly M2422)


4



0, 1, 3, 5, 7, 15, 45, 95, 235, 463, 733, 1437, 1583, 1677, 1803, 4163, 4765, 9219, 9959, 25477, 26059, 41539, 54195, 65057, 74977, 116589, 192289, 311835, 350767, 353635, 416337, 423253
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,3


REFERENCES

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..32.
H. C. Williams and C. R. Zarnke, Some prime numbers of the forms 2*3^n+1 and 2*3^n1, Math. Comp., 26 (1972), 995998.


PROG

(PARI) is(n)=ispseudoprime(4*3^n1) \\ Charles R Greathouse IV, Feb 20 2017


CROSSREFS

Sequence in context: A303027 A217615 A050553 * A155802 A080741 A247356
Adjacent sequences: A005537 A005538 A005539 * A005541 A005542 A005543


KEYWORD

nonn,hard


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from Robert G. Wilson v and from Jud McCranie
More terms from Borys Jaworski, Feb 13 2010
0 added by Vincenzo Librandi, Sep 26 2012


STATUS

approved



