A255682 Numbers k such that 4^k - 2^k - 3 is prime.
3, 7, 13, 15, 21, 73, 231, 301, 493, 895, 955, 4069, 5057, 5415, 15325, 19845, 21603, 24577, 37877, 40193, 44283
Offset: 1
Examples
3 is in this sequence because 4^3 - 2^3 - 3 = 53.
Crossrefs
Cf. A098845.
Programs
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Magma
[n: n in [1..800] | IsPrime(4^n-2^n-3)];
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Mathematica
Select[Range[15000], PrimeQ[4^# - 2^# - 3] &]
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PARI
for(n=1,500,if(ispseudoprime(4^n-2^n-3),print1(n,", "))) \\ Derek Orr, Mar 03 2015
Extensions
a(15)-a(21) from Hans Havermann, Jul 18 2015
Comments