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 A261578 #28 Sep 08 2022 08:46:13 %S A261578 1,2,5,8,11,23,26,59,83,89,116,1103,1568,5768,13376,17810,18614,66209, %T A261578 167933,188318 %N A261578 Numbers m such that (4^m + 17) / 3 is prime. %C A261578 After 1, m is of the form 3*k+2. In fact, for m = 3*k or 3*k+1, 4^n+17 is divisible by 9 and 7, respectively. [_Bruno Berselli_, Aug 26 2015] %C A261578 a(21) > 300000. - _Robert Price_, Apr 04 2017 %e A261578 2 is in the sequence because (4^2+17)/3 = 11 is prime. %e A261578 5 is in the sequence because (4^5+17)/3 = 347 is prime. %t A261578 Select[Range[0, 5000], PrimeQ[(4^# + 17)/3] &] %o A261578 (Magma) [n: n in [0..1000] | IsPrime((4^n+17) div 3)]; %o A261578 (PARI) for(n=1, 1e3, if(isprime((4^n+17)/3), print1(n", "))) \\ _Altug Alkan_, Sep 14 2015 %Y A261578 Cf. similar sequences listed in A261539. %K A261578 nonn,more %O A261578 1,2 %A A261578 _Vincenzo Librandi_, Aug 26 2015 %E A261578 a(14)-a(15) from _Vincenzo Librandi_, Sep 14 2015 %E A261578 a(16)-a(20) from _Robert Price_, Feb 01 2017