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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^n-1, Math. Comp., 26 (1972), 995-998.

PROG

(PARI) is(n)=ispseudoprime(4*3^n-1) \\ 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

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Last modified October 23 09:45 EDT 2019. Contains 328345 sequences. (Running on oeis4.)