A006553 Numbers k such that k*3^k - 1 is prime. (Formerly M1575)

1, 2, 6, 10, 18, 40, 46, 86, 118, 170, 1172, 1698, 1810, 2268, 4338, 18362, 72662, 88392, 94110, 161538, 168660, 292340, 401208, 560750, 1035092

Offset

1,2

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..25.

Steven Harvey, Generalized Woodall Search

Mathematica

Select[Range[10000], PrimeQ[# 3^# - 1] &] (* Vincenzo Librandi, Dec 02 2015 *)

Prog

(Magma) [n: n in [0..1420] | IsPrime(n*3^n-1)]; // Vincenzo Librandi, Dec 02 2015
(PARI) is(n)=ispseudoprime(n*3^n-1) \\ Charles R Greathouse IV, Feb 20 2017

Crossrefs

Sequence in context: A095357 A095358 A084481 * A054273 A127567 A360420

Adjacent sequences: A006550 A006551 A006552 * A006554 A006555 A006556

Keyword

hard,nonn

Author

N. J. A. Sloane

Extensions

More terms from Jud McCranie

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(24)-a(25) from Harvey link by Ray Chandler, Apr 10 2016

Status

approved