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 A067027 #18 Dec 15 2017 17:35:49 %S A067027 1,2,3,4,6,10,11,12,15,17,29,48,63,77,88,187,190,338,1133,1311,1832, %T A067027 2782,2907,3180,3272,5398,17530 %N A067027 Numbers n such that (prime(n)# + 4)/2 is a prime, where x# is the primorial A034386(x). %C A067027 Numbers n such that [A002110(n)/2]+2 is prime. %C A067027 These primes are products of consecutive odd primes plus 2: 2+[3.5.7.....p(n)] if n is here. %C A067027 a(19)-a(22) are Fermat and Lucas PRPs. (prime(2782)# + 4)/2 has 10865 digits. PFGW Version 1.2.0 for Windows [FFT v23.8] Primality testing (p(2782)#+4)/2 [N-1/N+1, Brillhart-Lehmer-Selfridge] Running N-1 test using base 5 Running N+1 test using discriminant 13, base 1+sqrt(13) (p(2782)#+4)/2 is Fermat and Lucas PRP! - _Jason Earls_, Dec 12 2006 %C A067027 a(28) > 25000. - _Robert Price_, Sep 29 2017 %t A067027 p = 1; Do[p = p*Prime[n]; If[PrimeQ[(p + 4)/2], Print[n]], {n, 1, 400} ] %t A067027 Flatten[Position[FoldList[Times,Prime[Range[3000]]],_?(PrimeQ[ (#+4)/2]&)]] (* _Harvey P. Dale_, May 24 2015 *) %o A067027 (PARI) n=0;pr=1/2;forprime(p=2,1e4,n++;pr*=p;if(ispseudoprime(pr+2),print1(n", "))) \\ _Charles R Greathouse IV_, Jul 25 2011 %Y A067027 Cf. A002110, A067024, A065026. %K A067027 nonn %O A067027 1,2 %A A067027 _Labos Elemer_, Dec 29 2001 %E A067027 More terms from _Robert G. Wilson v_, Dec 30 2001 %E A067027 a(19)-a(22) from _Jason Earls_, Dec 12 2006 %E A067027 a(23) from _Ray Chandler_, Jun 16 2013 %E A067027 a(24)-a(27) from _Robert Price_, Sep 29 2017