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 A264886 #13 Nov 28 2015 19:16:55 %S A264886 1,2,3,4,5,8,9,15,25,36,57,80,81,133,225,281,282,288,343,632,653 %N A264886 Integers n such that A061720(n-1) + 1 or A061720(n-1) - 1 is prime. %C A264886 Integers n such that A002110(n) - A002110(n-1) + 1 or A002110(n) - A002110(n-1) - 1 is prime. %C A264886 Are there any other squares in sequence? %e A264886 a(3) = 3 because 2*3*5 - 2*3 - 1 = 23 is prime. %e A264886 a(6) = 8 because 2*3*5*7*11*13*17*19 - 2*3*5*7*11*13*17 + 1 = 9189181 is prime. %t A264886 t = Differences[FoldList[Times, 1, Prime@ Range@ 1200]]; Select[Range@ 360, Or[PrimeQ[t[[# - 1]] + 1], PrimeQ[t[[# - 1]] - 1]] &] - 1 (* _Michael De Vlieger_, Nov 28 2015, after _Alonso del Arte_ at A061720 *) %o A264886 (PARI) a(n) = prod(k=1, n, prime(k)); %o A264886 for(n=0, 1e3, if(ispseudoprime(a(n)-a(n-1)-1) || ispseudoprime(a(n)-a(n-1)+1), print1(n, ", "))) %Y A264886 Cf. A002110, A061720. %K A264886 nonn,more %O A264886 1,2 %A A264886 _Altug Alkan_, Nov 27 2015