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A227447
Numbers k such that 3*5^(2*k) - 3*5^k + 1 is prime.
0
1, 2, 8, 25, 41, 66, 108, 318, 498, 546, 557, 846, 3780, 26370, 29305, 31482, 32905
OFFSET
1,2
COMMENTS
a(14) > 10^4. - Daniel Suteu, Feb 13 2019
LINKS
Eric L. F. Roettger, A Cubic Extension of the Lucas Functions, Ph. D. Dissertation, Dept. Math. and Statistics, Univ. Calgary, 2009 (see page 196).
MATHEMATICA
Select[Range[0, 3000], PrimeQ[3 5^(2 #) - 3 5^# + 1]&]
PROG
(PARI) is(n)=ispseudoprime(3*5^(2*n)-3*5^n+1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Cf. A057917.
Sequence in context: A309088 A070944 A278836 * A077167 A062450 A198181
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Jul 14 2013
EXTENSIONS
a(13) from Daniel Suteu, Feb 13 2019
a(14)-a(17) from Michael S. Branicky, Oct 08 2024
STATUS
approved