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 A230537 #15 Apr 03 2023 10:36:13
%S A230537 1,2,6,13,22,29,30,33,36,50,61,118,180,226,405,433,522,789,929,960,
%T A230537 1026,1030,1118,1266,1521,1718,2536,3029,3366,4253,9157,10165,23641,
%U A230537 29877,30648,47265,56097,90501,101981,103021,108370,117909,157237,169156,174168
%N A230537 Numbers n such that 3^7*2^n - 1 is prime.
%C A230537 Riesel Primes with k = 3^7 = 2187.
%C A230537 Checked up to n = 1000000.
%H A230537 Lei Zhou, <a href="/A230537/b230537.txt">Table of n, a(n) for n = 1..52</a>
%H A230537 K. Bonath, <a href="http://www.rieselprime.de/">Riesel Prime Database</a>
%H A230537 C. K. Caldwell, <a href="https://t5k.org/primes/page.php?id=88600">a(51) = 2187*2^449776-1</a>
%H A230537 C. K. Caldwell, <a href="https://t5k.org/primes/page.php?id=92500">a(52) = 2187*2^916686-1</a>
%H A230537 C. K. Caldwell, <a href="https://t5k.org/primes/page.php?id=94391">a(53) = 2187*2^992632-1</a>
%e A230537 2187*2^1-1=4373 is a prime number.
%t A230537 b=3^7;i=0; Table[While[i++; cp=b*2^i-1; !PrimeQ[cp]]; i, {j, 1, 30}]
%o A230537 (PARI) is(n)=ispseudoprime(3^7*2^n-1) \\ _Charles R Greathouse IV_, May 22 2017
%Y A230537 Cf. A002235, A002236, A050539, A050566, A050880, A230527.
%K A230537 nonn,hard
%O A230537 1,2
%A A230537 _Lei Zhou_, Oct 22 2013
%E A230537 _Lei Zhou_, Nov 08 2013, added a Mathematica program for small elements.