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 A081618 #23 Oct 01 2020 08:39:06
%S A081618 1,7,232,430
%N A081618 Numbers n such that (product of first n primes)+1 is divisible by the (n+1)-th prime. Also n such that A075306(n)-1 is equal to A002110(n). Positions of 1 in A081617.
%C A081618 a(5) is greater than 10^7. - _Matty Muir_, Oct 01 2020
%e A081618 The 8th prime, 19, divides 2*3*5*7*11*13*17+1=510511, thus 7 is a member.
%t A081618 With[{nn=500},Flatten[Position[Thread[{Rest[FoldList[Times,1,Prime[ Range[ nn]]]]+ 1, Prime[ Range[2,nn+1]]}],_?(Divisible[#[[1]],#[[2]]]&),{1},Heads->False]]] (* _Harvey P. Dale_, Apr 18 2015 *)
%o A081618 (PARI) p=1; for(n=1, 10^5, p=p*prime(n); if((p+1)%prime(n+1)==0, print1(n", ")))
%Y A081618 Cf. A066735.
%K A081618 nonn,hard,more
%O A081618 1,2
%A A081618 _Ralf Stephan_, Mar 24 2003