cp's OEIS Frontend

A247957 Numbers k such that 33^k + 2 is prime.

%I A247957 #38 Jul 10 2025 19:39:31
%S A247957 0,2,26,60,218,248,399,1175,1244,2670,9300,45216,144412
%N A247957 Numbers k such that 33^k + 2 is prime.
%C A247957 Some terms correspond to probable primes. Lifchitz link shows that _Ray Chandler_ discovered 9300, and Lelio R Paula found that 45216 is in the sequence. - _Jens Kruse Andersen_, Sep 29 2014
%C A247957 Terms in the similar sequence, 53^k+2, begin with 0, 7, 14483 with the next term > 2*10^5. - _Robert Price_, Mar 28 2015
%C A247957 Confirmed that 45216 is a(12). - _Robert Price_, Apr 14 2015
%C A247957 a(14) > 2*10^5. - _Robert Price_, Apr 14 2015
%H A247957 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=33^n%2B2&amp;action=Search">PRP Records, search for 33^n+2</a>
%p A247957 A247957:=n->`if`(isprime(33^n+2),n,NULL): seq(A247957(n), n=0..1000); # _Wesley Ivan Hurt_, Sep 28 2014
%t A247957 Select[Range[0,1000], PrimeQ[33^# + 2] &]
%o A247957 (Magma) [n: n in [0..350]| IsPrime( 33^n + 2 )];
%o A247957 (PARI) is(n)=ispseudoprime(33^n+2) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y A247957 Cf. numbers n such that k^n+2 is prime: A051783 (k=3), A087885 (k=5), A090649 (k=9), A109076 (k=11), A138048 (k=15), A113480 (k=17), A138049 (k=21), A138050 (k=23), A138051 (k=27), A087886 (k=29), this sequence (k=33), A247958 (k=35), A247959 (k=39), A247960 (k=41), A247961 (k=45); (0, 113) for k=47; A247962 (k=51); A247963 (k=57), A113481 (k=59).
%K A247957 nonn,more
%O A247957 1,2
%A A247957 _Vincenzo Librandi_, Sep 28 2014
%E A247957 a(8)-a(11) from _Jens Kruse Andersen_, Sep 29 2014
%E A247957 a(12)-a(13) from _Robert Price_, Apr 14 2015