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 A359490 #11 Mar 13 2023 06:00:58 %S A359490 4363,13729,31607,6973007,208969199 %N A359490 Primes p followed by two or more 2-pseudoprimes (A001567) before the next prime. %C A359490 Is this sequence infinite? Is there a prime followed by three pseudoprimes before the next prime? I believe heuristics suggest "no" to both. %C A359490 From _Amiram Eldar_, Mar 12 2023: (Start) %C A359490 The primes preceding the terms of A335326. %C A359490 There are no more terms below 2^64. (End) %e A359490 a(n): pseudoprimes following a(n) %e A359490 4363: 4369, 4371 %e A359490 13729: 13741, 13747 %e A359490 31607: 31609, 31621 %e A359490 6973007: 6973057, 6973063 %e A359490 208969199: 208969201, 208969223 %o A359490 (PARI) prp(n,a=2)=Mod(a,n)^(n-1)==1 %o A359490 list(lim)=my(v=List(),p=3); forprime(q=5,lim, my(s=0); forstep(k=p+2,q-2,2, if(prp(k) && s++>1, listput(v,p))); p=q); Vec(v) %Y A359490 Cf. A001567, A335326. %K A359490 nonn,more %O A359490 1,1 %A A359490 _Charles R Greathouse IV_, Mar 07 2023