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 A274551 #46 Jul 28 2025 06:20:52 %S A274551 4,8925,32445,442365 %N A274551 Numbers k such that sigma(k) == 0 (mod k+3). %C A274551 a(5) > 10^8 if it exists. - _Felix Fröhlich_, Jul 01 2016 %C A274551 No more terms < 6.5*10^14. - _Jud McCranie_, Dec 02 2019 %C A274551 No more terms < 2.7*10^15. - _Jud McCranie_, Jul 27 2025 %e A274551 sigma(4) mod (4+3) = 7 mod 7 = 0. %t A274551 Select[Range[10^6], Mod[DivisorSigma[1, #], # + 3] == 0 &] (* _Michael De Vlieger_, Jul 01 2016 *) %o A274551 (PARI) is(n) = Mod(sigma(n), n+3)==0 \\ _Felix Fröhlich_, Jul 01 2016 %o A274551 (Magma) [n: n in [1..2*10^6] | SumOfDivisors(n) mod (n+3) eq 0 ]; // _Vincenzo Librandi_, Jul 02 2016 %Y A274551 Cf. A000203, A067702, A087167, A088834, A274552, A274553, A274554, A274556. %K A274551 nonn,more %O A274551 1,1 %A A274551 _Paolo P. Lava_, Jun 28 2016