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 A275998 #15 Sep 08 2022 08:46:17 %S A275998 3,27,267,8820000 %N A275998 Numbers n such that phi(n^2-1) = phi(n^2+1). %C A275998 No other terms below 10^8. - _Michel Marcus_, Aug 17 2016 %e A275998 3 is a term because phi(3^2-1) = phi(3^2+1). %t A275998 Select[Range@10000000, EulerPhi@(#^2 - 1) == EulerPhi[#^2 + 1] &] (* _Vincenzo Librandi_, Aug 18 2016 *) %o A275998 (PARI) isok(n) = eulerphi(n^2-1) == eulerphi(n^2+1); \\ _Michel Marcus_, Aug 16 2016 %o A275998 (Magma) [n: n in [2..100000] | EulerPhi(n^2-1) eq EulerPhi(n^2+1)]; // _Vincenzo Librandi_, Aug 18 2016 %Y A275998 Cf. A000010, A066812. %K A275998 nonn,more %O A275998 1,1 %A A275998 _Altug Alkan_, Aug 16 2016