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

1,1

Comments

a(22) > 150000. - Hans Havermann, Jul 18 2015

Links

Table of n, a(n) for n=1..21.

Example

3 is in this sequence because 4^3 - 2^3 - 3 = 53.

Mathematica

Select[Range[15000], PrimeQ[4^# - 2^# - 3] &]

Prog

(Magma) [n: n in [1..800] | IsPrime(4^n-2^n-3)];
(PARI) for(n=1, 500, if(ispseudoprime(4^n-2^n-3), print1(n, ", "))) \\ Derek Orr, Mar 03 2015

Crossrefs

Cf. A098845.

Sequence in context: A209839 A192854 A002236 * A080565 A164344 A002254

Adjacent sequences: A255679 A255680 A255681 * A255683 A255684 A255685

Keyword

nonn,more

Author

Vincenzo Librandi, Mar 02 2015

Extensions

a(15)-a(21) from Hans Havermann, Jul 18 2015

Status

approved