OFFSET
1,2
COMMENTS
No further terms < 10^5.
EXAMPLE
1 is in this sequence because 2*1*3^1 - 1 = 5 is prime.
MAPLE
A271956:=n->`if`(isprime(2*n*3^n-1), n, NULL): seq(A271956(n), n=1..2*10^3); # Wesley Ivan Hurt, Apr 17 2016
MATHEMATICA
Select[Range[10000], PrimeQ[2 # 3^# - 1] &]
PROG
(PARI) is(n)=ispseudoprime(2*n*3^n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Ray Chandler, Apr 17 2016
STATUS
approved