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 A247147 #30 Sep 08 2022 08:46:09 %S A247147 2,3,5,7,17,19,31,61,89,107,521,1279,9689,9941,21701,23209,216091, %T A247147 13466917,30402457,57885161 %N A247147 Numbers k such that 3*k-4 and 2^k-1 are prime. %C A247147 All terms are primes. %H A247147 Ben Green and Terence Tao, <a href="https://arxiv.org/abs/math/0404188">The primes contain arbitrarily long arithmetic progressions</a>, arXiv:math/0404188 [math.NT], 2004-2007; Annals of Mathematics, 167 (2008), pp. 481-547. %t A247147 Select[Range[10000], PrimeQ[2^# - 1] && PrimeQ[3 # - 4] &] %o A247147 (Magma) [n: n in [0..10000] | IsPrime(3*n-4) and IsPrime(2^n-1)]; %o A247147 (Python) %o A247147 from sympy import isprime %o A247147 from itertools import count, islice %o A247147 def agen(startk=1): %o A247147 for k in count(startk): %o A247147 if isprime(3*k-4) and isprime(2**k-1): %o A247147 yield k %o A247147 print(list(islice(agen(), 12))) # _Michael S. Branicky_, Jul 31 2022 %Y A247147 Cf. A000043, A001348, A228121. %K A247147 nonn,more %O A247147 1,1 %A A247147 _Vincenzo Librandi_, Nov 21 2014 %E A247147 a(20) using A000043 from _Michael S. Branicky_, Jul 31 2022