This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A217380 #22 Sep 15 2024 14:31:54 %S A217380 13,661,773,833,4273,40613,302913 %N A217380 Numbers k such that 8^k - 7 is prime. %C A217380 All terms are equal to 1/3 of the multiples of 3 in A059609. %C A217380 Naturally these numbers are odd since (9-1)^(2n)-7 is divisible by 3. - _Bruno Berselli_, Oct 04 2012 %t A217380 Select[Range[4000], PrimeQ[8^# - 7] &] %o A217380 (PARI) is(n)=ispseudoprime(8^n-7) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A217380 Cf. A059609, A217353, A217356. %K A217380 nonn,more %O A217380 1,1 %A A217380 _Vincenzo Librandi_, Oct 02 2012 %E A217380 a(7) using A059609 from _Michael S. Branicky_, Sep 15 2024