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 A261577 #45 Sep 08 2022 08:46:13 %S A261577 1,4,10,34,40,106,418,682,12702,30484,182026,217720,241306 %N A261577 Numbers m such that (4^m + 11) / 3 is prime. %C A261577 From _Bruno Berselli_, Aug 26 2015: (Start) %C A261577 After 1, m is always even (for m odd 4^m+11 is divisible by 5). %C A261577 Let m = 2*h. For h = 3*k+1, 9*k+3, 11*k+2, 11*k+8, 13*k+8, 19*k+6, 23*k+10, 23*k+14 and 29*k+28, 4^m+11 is divisible by 9, 37, 89, 23, 53, 229, 47, 1013 and 59, respectively. (End) %C A261577 All terms appear to be of the form 3*k+1. - _Dhilan Lahoti_, Aug 31 2015 %C A261577 12702 is the first counterexample to Dhilan Lahoti's conjecture: 12702 = 3*4234. - _Bruno Berselli_, Feb 02 2017 %C A261577 a(14) > 300,000. - _Robert Price_, Mar 18 2017 %e A261577 4 is in the sequence because (4^4+11)/3 = 89 is prime. %e A261577 10 is in the sequence because (4^10+11)/3 = 349529 is prime. %t A261577 Select[Range[0, 5000], PrimeQ[(4^# + 11)/3] &] %o A261577 (Magma) [n: n in [0..1500] | IsPrime((4^n+11) div 3)]; %o A261577 (PARI) is(n)=isprime((4^n + 11) / 3) \\ _Anders Hellström_, Aug 31 2015 %Y A261577 Cf. A163868. %Y A261577 Cf. similar sequences listed in A261539. %K A261577 nonn,more %O A261577 1,2 %A A261577 _Vincenzo Librandi_, Aug 26 2015 %E A261577 a(9)-a(12) from _Robert Price_, Feb 01 2017 %E A261577 a(13) from _Robert Price_, Mar 18 2017