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 A006552 Numbers k such that k*3^k + 1 is prime. (Formerly M1848) 8
 2, 8, 32, 54, 114, 414, 1400, 1850, 2848, 4874, 7268, 19290, 337590, 1183414 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES H. Dubner, Generalized Cullen numbers, J. Rec. Math., 21 (No. 3, 1989), 190-191. 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..14. H. Dubner, Generalized Cullen numbers, J. Rec. Math., 21 (No. 3, 1989), 190-191. (Annotated scanned copy) G. Loeh, Generalized Cullen primes MATHEMATICA Select[Range[10000], PrimeQ[# 3^# + 1] &] (* Vincenzo Librandi, Dec 02 2015 *) PROG (Magma) [n: n in [0..420] | IsPrime(n*3^n+1)]; // Vincenzo Librandi, Dec 02 2015 (PARI) is(n)=ispseudoprime(n*3^n+1) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Sequence in context: A026369 A269818 A331823 * A134753 A212892 A302936 Adjacent sequences: A006549 A006550 A006551 * A006553 A006554 A006555 KEYWORD nonn,hard AUTHOR N. J. A. Sloane EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008 a(14) from Loeh link by Ray Chandler, Apr 10 2016 STATUS approved

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Last modified July 22 16:55 EDT 2024. Contains 374540 sequences. (Running on oeis4.)