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 A055971 #13 Apr 29 2024 09:09:12
%S A055971 1,198,294,20280,195320,1782240,3038720,12190720
%N A055971 Numbers k such that k | (sigma(k) - d(k) - phi(k)) and k is not a prime or twice a prime.
%C A055971 a(9) > 10^10, if it exist. - _Amiram Eldar_, Apr 29 2024
%t A055971 Do[ If[ And[ !PrimeQ[ n ], !PrimeQ[ n/2 ] ], If[ Mod[ DivisorSigma[ 1, n ]-DivisorSigma[ 0, n ]- EulerPhi[ n ], n ]==0, Print[ n ] ] ], {n, 1, 10^8} ]
%o A055971 (PARI) is1(k) = {my(f = factor(k)); !((sigma(f) - numdiv(f) - eulerphi(f)) % k);}
%o A055971 is(k) = !isprime(k) && !(!(k%2) && isprime(k/2)) && is1(k); \\ _Amiram Eldar_, Apr 29 2024
%Y A055971 Cf. A000005 (d(n)), A000010 (phi), A000203 (sigma).
%K A055971 nonn,more
%O A055971 1,2
%A A055971 _Robert G. Wilson v_, Jul 19 2000