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 A224221 #13 Dec 12 2015 12:32:09 %S A224221 3,5,7,13,29,37,41,61,53,131,43,19,277,379,137,239,79,157,331,71 %N A224221 a(0)=3; for n>0, a(n) is the smallest odd prime q not already in the sequence such that the n-th prime p(n) divides a(n-1)+q. If no such prime q exists, the sequence terminates. %C A224221 a(20) does not exist, so the sequence terminates. A134204 is a similar sequence for which the termination question is unresolved. %e A224221 After a(3)=13, to find a(4) we look for an odd prime q such that the fourth prime, 7, divides 13+q, and q=29 works, since 7 divides 13+29 = 42. %e A224221 After a(19)=71 we look for an odd prime q such that p(20)=71 divides 71+q. The only candidate is q=71. Since 71 is already in the sequence, the sequence terminates. %Y A224221 Cf. A134204, A224222. %K A224221 nonn,fini,full %O A224221 0,1 %A A224221 _Daniel Drucker_ and _N. J. A. Sloane_, Apr 05 2013