A056801 Numbers k such that 4*9^k + 1 is prime.

0, 1, 3, 7, 627, 1653, 1761, 4801, 36349

Offset

1,3

Links

Table of n, a(n) for n=1..9.

Mathematica

Do[ If[ PrimeQ[ 4*9^n + 1], Print[ n ]], {n, 0, 10^4}] (* Ryan Propper, Mar 25 2007 *)
Select[Range[0, 5000], PrimeQ[4 9^#+1]&] (* Harvey P. Dale, Dec 07 2011 *)

Prog

(PARI) is(n)=ispseudoprime(4*9^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A120905 A062599 A101246 * A302987 A092568 A055624

Adjacent sequences: A056798 A056799 A056800 * A056802 A056803 A056804

Keyword

nonn,more

Author

Robert G. Wilson v, Aug 22 2000

Extensions

a(6)-a(8) from Ryan Propper, Mar 25 2007

a(9) from Michael S. Branicky, Aug 11 2024

Status

approved