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 A054984 #19 Mar 09 2025 12:28:27
%S A054984 427,553,595,623,737,871,913,923,1199,1207,1241,1507,1582,1817,1848,
%T A054984 2193,2226,2337,2398,2407,2553,2561,2728,2758,2929,3016,3115,3248,
%U A054984 3346,3502,3503,3598,3705,3762,4171,4293,4343,4462,4587,4633,4841,4867,4984
%N A054984 Composite numbers k such that sigma(k + 6!) = sigma(k + 720) = sigma(k) + 720.
%H A054984 Amiram Eldar, <a href="/A054984/b054984.txt">Table of n, a(n) for n = 1..6000</a>
%e A054984 553 is a term because sigma(553) + 720 = 640 + 720 = 1360 = sigma(553 + 720) = sigma(1273) = 1 + 19 + 67 + 1273.
%t A054984 Select[Range[5000], CompositeQ[#] && Differences@ DivisorSigma[1, {#, # + 720}] == {720} &] (* _Amiram Eldar_, Mar 09 2025 *)
%o A054984 (PARI) isok(k) = !isprime(k) && sigma(k + 720) == sigma(k) + 720; \\ _Amiram Eldar_, Mar 09 2025
%Y A054984 Cf. A015914, A015915, A015916, A015917, A033560, A033561, A054799.
%K A054984 nonn
%O A054984 1,1
%A A054984 _Labos Elemer_, May 29 2000