A271956 Numbers n such that 2*n*3^n - 1 is prime.

1, 4, 6, 10, 35, 112, 149, 390, 424, 566, 660, 664, 850, 1414, 1436, 1497, 1524, 1904, 5116, 6625, 10944, 12637, 35691, 92304

Offset

1,2

Comments

No further terms < 10^5.

Links

Table of n, a(n) for n=1..24.

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

Cf. A006553, A266694.

Sequence in context: A242565 A032392 A253048 * A242502 A136838 A234276

Adjacent sequences: A271953 A271954 A271955 * A271957 A271958 A271959

Keyword

nonn,more

Author

Ray Chandler, Apr 17 2016

Status

approved