A005540 Numbers k such that 4*3^k - 1 is prime.

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

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• hard

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• 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.

Programs

PARI

is(n)=ispseudoprime(4*3^n-1) \\ Charles R Greathouse IV, Feb 20 2017

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