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 A196940 #26 Feb 24 2025 22:43:11
%S A196940 29,59,239,479,15359,245759,1966079,32212254719,32985348833279,
%T A196940 141670994486089356410879,18133887294219437620592639,
%U A196940 72535549176877750482370559,1246151246048358630847319119012823039,638029437976759618993827388934565396479,669022355955918694246071548179450845179412479
%N A196940 Primes of the form 15*2^k - 1.
%H A196940 Vincenzo Librandi, <a href="/A196940/b196940.txt">Table of n, a(n) for n = 1..28</a>
%F A196940 a(n) = A196305(A002237(n)). - _Elmo R. Oliveira_, Feb 23 2025
%t A196940 Select[Table[15 2^n - 1, {n, 1, 300}], PrimeQ] (* _Vincenzo Librandi_, Feb 23 2014 *)
%o A196940 (PARI) for(n=1,1e3,if(ispseudoprime(t=15<<n-1),print1(t", "))) \\ _Charles R Greathouse IV_, Oct 08 2011
%o A196940 (Magma) [a: n in [1..130] | IsPrime(a) where a is 15*2^n-1]; // _Vincenzo Librandi_, Feb 23 2014
%Y A196940 Primes in A196305.
%Y A196940 Cf. A002237 (k such that 15*2^k-1 is prime).
%K A196940 nonn
%O A196940 1,1
%A A196940 _Brad Clardy_, Oct 07 2011