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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

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 February 27 15:59 EST 2020. Contains 332307 sequences. (Running on oeis4.)