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 A207575 #31 Nov 06 2023 11:28:23 %S A207575 1,390,10374,2283934267736070,7316037865689066623729670 %N A207575 Numbers k such that phi(k) + 2 divides k + 2 and k is not twice a prime. %C A207575 Contains 2 * terms t of A350777 such that (t-3)/phi(t) = 2. - _Max Alekseyev_, Oct 26 2023 %t A207575 Select[Range[20000000], !PrimeQ[#/2] && Divisible[#+2, EulerPhi[#]+2]&] %o A207575 (PARI) for(n=1,1e5,if((n+2)%(eulerphi(n)+2)==0&&(n%2||!isprime(n/2)), print1(n", "))) \\ _Charles R Greathouse IV_, Mar 02 2012 %Y A207575 Cf. A000010, A207574, A202855, A203966, A350777. %K A207575 nonn,more,hard %O A207575 1,2 %A A207575 _José María Grau Ribas_, Feb 19 2012 %E A207575 a(4)-a(5) from _Max Alekseyev_, Nov 06 2023