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 A228027 #31 Nov 29 2023 07:03:41
%S A228027 13,73,1033,262153,1073741833,73786976294838206473,
%T A228027 4835703278458516698824713
%N A228027 Primes of the form 4^k + 9.
%C A228027 Subsequence of A104070. - _Elmo R. Oliveira_, Nov 28 2023
%H A228027 Vincenzo Librandi, <a href="/A228027/b228027.txt">Table of n, a(n) for n = 1..12</a>
%F A228027 a(n) = 4^A217350(n) + 9. - _Elmo R. Oliveira_, Nov 28 2023
%e A228027 262153 is a term because 4^9 + 9 = 262153 is prime.
%t A228027 Select[Table[4^n + 9, {n, 0, 200}],PrimeQ]
%o A228027 (Magma) [a: n in [0..200] | IsPrime(a) where a is 4^n+9];
%Y A228027 Cf. A000040, A217350 (corresponding k's).
%Y A228027 Cf. Primes of the form r^k + h: A092506 (r=2, h=1), A057733 (r=2, h=3), A123250 (r=2, h=5), A104066 (r=2, h=7), A104070 (r=2, h=9), A057735 (r=3, h=2), A102903 (r=3, h=4), A102870 (r=3, h=8), A102907 (r=3, h=10), A290200 (r=4, h=1), A228026 (r=4, h=3), this sequence (r=4, h=9), A182330 (r=5, h=2), A228029 (r=5, h=6), A102910 (r=5, h=8), A182331 (r=6, h=1), A104118 (r=6, h=5), A104115 (r=6, h=7), A104065 (r=7, h=4), A228030 (r=7, h=6), A228031 (r=7, h=10), A228032 (r=8, h=3), A228033 (r=8, h=5), A144360 (r=8, h=7), A145440 (r=8, h=9), A228034 (r=9, h=2), A159352 (r=10, h=3), A159031 (r=10, h=7).
%K A228027 nonn,easy
%O A228027 1,1
%A A228027 _Vincenzo Librandi_, Aug 11 2013
%E A228027 Corrected cross-references - _Robert Price_, Aug 01 2017