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A056801
Numbers k such that 4*9^k + 1 is prime.
0
0, 1, 3, 7, 627, 1653, 1761, 4801, 36349
OFFSET
1,3
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
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