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 A265121 #23 Oct 08 2024 17:28:06 %S A265121 0,1,3,5,11,15,17,153,169,273,317,373,923,1403,1969,2349,7809,10313, %T A265121 12291,24865,41289 %N A265121 Integers k such that k*3^k + 2 is prime. %C A265121 Initial corresponding primes are 2, 5, 83 and 1217. %C A265121 How do this sequence and A006552 compare asymptotically? %C A265121 a(22) > 10^5. - _Michael S. Branicky_, Oct 08 2024 %e A265121 a(3) = 3 because 3^3 * 3 + 2 = 83 is prime. %t A265121 Select[Range[0, 10000], PrimeQ[# 3^# + 2] &] (* _Vincenzo Librandi_, Dec 02 2015 *) %o A265121 (PARI) for(n=0, 1e6, if(ispseudoprime(3^n*n + 2), print1(n, ", "))); %o A265121 (Magma) [n: n in [0..400] | IsPrime(n*3^n+2)]; // _Vincenzo Librandi_, Dec 02 2015 %Y A265121 Cf. A006552, A036290, A182373. %K A265121 nonn,hard,more %O A265121 1,3 %A A265121 _Altug Alkan_, Dec 01 2015 %E A265121 a(1) = 0 added by _Vincenzo Librandi_, Dec 02 2015 %E A265121 a(21) from _Michael S. Branicky_, May 16 2023