A227447 Numbers k such that 3*5^(2*k)-3*5^k+1 is prime.

1, 2, 8, 25, 41, 66, 108, 318, 498, 546, 557, 846, 3780

Offset

1,2

Comments

a(14) > 10^4. - Daniel Suteu, Feb 13 2019

Links

Table of n, a(n) for n=1..13.

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

Adjacent sequences: A227444 A227445 A227446 * A227448 A227449 A227450

Keyword

nonn,more

Author

Vincenzo Librandi, Jul 14 2013

Extensions

a(13) from Daniel Suteu, Feb 13 2019

Status

approved