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URL: https://oeis.org/A006553

⇱ A006553 - OEIS

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A006553
Numbers k such that k*3^k - 1 is prime.
14
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).
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 * A370048 A054273 A127567
KEYWORD
nonn,hard,more
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