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A182373 Positive integers n such that n*3^n - 2 is prime. 1
3, 5, 7, 37, 45, 53, 179, 277, 721, 2087, 6197, 6317, 8775, 12781 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Similar to A060353, and to the Woodall primes, A050918. The next term in the sequence is unknown; if the sequence is infinite, the next term is greater than 5000.

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

79 = 3*3^3 - 2; 1213 = 5*3^5 - 2; 15307 = 7*3^7 - 2.

MAPLE

#choose N large, then S is the desired set

f:=n->n*3^n - 2:

S:={}:

for n from 0 to N do if(isprime(f(n))) then S:=S union {n}: fi: od

MATHEMATICA

Select[Range[2100], PrimeQ[#*3^# - 2] &] (* Jayanta Basu, Jun 01 2013 *)

PROG

PARI) for(n=1, 1e6, if(ispseudoprime(3^n*n - 2), print1(n, ", "))) \\ Altug Alkan, Dec 01 2015

CROSSREFS

Cf. A050918, A060353.

Sequence in context: A154544 A155034 A126359 * A087363 A234569 A037287

Adjacent sequences:  A182370 A182371 A182372 * A182374 A182375 A182376

KEYWORD

nonn

AUTHOR

Patrick Devlin, Apr 26 2012

EXTENSIONS

a(11)-a(14) from Altug Alkan, Dec 01 2015

STATUS

approved

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Last modified March 21 20:25 EDT 2019. Contains 321382 sequences. (Running on oeis4.)