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.
isok(n) = {my(pp=prod(k=1, n, prime(k))); isprime(pp*prime(n+1) - pp + 1);} \\ Michel Marcus, Sep 20 2019
1 is a term since A002110(2) - A002110(1) - A002110(0) - 1 = 6 - 2 - 1 - 1 = 2.
{1}~Join~Flatten[Position[Partition[Rest[FoldList[Times,1,Prime[Range[210]]]],3,1],?(PrimeQ[#[[3]]-#[[2]]-#[[1]]-1]&),{1},Heads->False]]+1 (* This generates the first 18 terms of the sequence. To generate the 19th term, change the Range constant to 4410, but it will take a very long time to run. *) (* _Harvey P. Dale, Apr 23 2014 *)
isok(k) = ispseudoprime(vecprod(primes(k+1)) - vecprod(primes(k)) - vecprod(primes(k-1)) - 1); \\ Michel Marcus, May 07 2025
Flatten[Position[#[[3]]-#[[2]]-#[[1]]+1&/@Partition[FoldList[Times,1,Prime[ Range[ 6700]]] ,3,1],?PrimeQ]] (* _Harvey P. Dale, Jul 25 2013 *)
Flatten[Position[Partition[Rest[FoldList[Times,1,Prime[Range[ 600]]]],3,1], ?(PrimeQ[#[[3]]+#[[2]]-#[[1]]-1]&),{1},Heads-> False]]+1 (* _Harvey P. Dale, May 26 2013 *)
Flatten[Position[Partition[FoldList[Times,Prime[Range[1350]]],3,1],?(PrimeQ[ #[[2]]+#[[3]]-#[[1]]+1]&),1,Heads->False]]+1 (* _Harvey P. Dale, May 30 2018 *)
P(n) = factorback(primes(n)); \\ A002110 isok(k) = ispseudoprime(P(k+1)+P(k)-P(k-1)+1); \\ Michel Marcus, Sep 11 2022