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 A215565 #10 Feb 23 2020 04:49:14 %S A215565 3281,432821,973241,1551941,1683683,1898999,2202257,2545181,2586083, %T A215565 2795519,3020093,3028133,4042403,4099439,4561481,4923521,5087171, %U A215565 5173601,5193161,5774801,6710177,8243111,9846401 %N A215565 Strong pseudoprimes to base 3 of the form 6*k-1. %C A215565 Motivated by the fact that most strong pseudoprimes to base 3 (A020229) are of the form 6*k+1. %H A215565 Amiram Eldar, <a href="/A215565/b215565.txt">Table of n, a(n) for n = 1..2621</a> (calculated from the b-file at A020229) %o A215565 (PARI) forstep(n=5,1e7,6,is_A020229(n) & print1(n",")) %Y A215565 Cf. A020229. %K A215565 nonn %O A215565 1,1 %A A215565 _M. F. Hasler_, Aug 16 2012