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 A006552 Numbers n such that n*3^n + 1 is prime. (Formerly M1848) 7
 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 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: A071389 A026369 A269818 * A134753 A212892 A227971 Adjacent sequences:  A006549 A006550 A006551 * A006553 A006554 A006555 KEYWORD nonn,hard,changed AUTHOR 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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