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
Examples
1 is in this sequence because 2*1*3^1 - 1 = 5 is prime.
Programs
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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
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Mathematica
Select[Range[10000], PrimeQ[2 # 3^# - 1] &]
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PARI
is(n)=ispseudoprime(2*n*3^n-1) \\ Charles R Greathouse IV, Jun 13 2017
Comments