A005540 - OEIS

A005540

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

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

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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: A217615 A334084 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