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 A269835 #30 Sep 13 2024 15:58:06
%S A269835 2,5,17,257,65537,549755813881
%N A269835 Primes p of the form 2^k + 4*(-1)^k - 3.
%C A269835 a(7) has 216 digits (see b-file).
%C A269835 Fermat primes > 3 from A019434 are terms.
%C A269835 Corresponding values of k: 0, 2, 4, 8, 16, 39, 715, ....
%C A269835 Note that for k = 1, 2^k + 4*(-1)^k - 3 = -5.
%C A269835 For further k values, see A059609. (2^k-7 is divisible by 3 for even k.) - _Jeppe Stig Nielsen_, Nov 18 2019
%H A269835 Jeppe Stig Nielsen, <a href="/A269835/b269835.txt">Table of n, a(n) for n = 1..10</a> (terms 1..7 from Jaroslav Krizek).
%t A269835 Select[Table[2^k+4(-1)^k-3,{k,0,50}],Positive[#]&&PrimeQ[#]&] (* _Harvey P. Dale_, Sep 14 2019 *)
%o A269835 (Magma) [2] cat [2^k + 4*(-1)^k - 3: k in [2..300] | IsPrime(2^k + 4*(-1)^k - 3)];
%o A269835 (PARI) for (k=0,40,my(j=2^k+4*(-1)^k-3);if(isprime(j),print1(j,", "))) \\ _Hugo Pfoertner_, Nov 21 2019
%Y A269835 Cf. A019434, A059609.
%K A269835 nonn
%O A269835 1,1
%A A269835 _Jaroslav Krizek_, Mar 06 2016