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 A223608 #23 Sep 08 2022 08:46:04 %S A223608 19,33,105,33705,33624064,2199041081344 %N A223608 Numbers n whose deficiency is 18: sigma(n) - 2*n = -18. %C A223608 Suggested by _N. J. A. Sloane_ and _Robert G. Wilson v_. %C A223608 a(6) > 10^12. %C A223608 a(7) > 10^13. - _Giovanni Resta_, Mar 29 2013 %C A223608 a(7) > 10^18. - _Hiroaki Yamanouchi_, Aug 21 2018 %C A223608 Any term x of this sequence can be combined with any term y of A223610 to satisfy the property (sigma(x)+sigma(y))/(x+y) = 2, which is a necessary (but not sufficient) condition for two numbers to be amicable. - _Timothy L. Tiffin_, Sep 13 2016 %e A223608 n = 33624064. sigma(n)-2*n = -18. %t A223608 Select[Range[1, 10^8], DivisorSigma[1, #] - 2 # == - 18 &] (* _Vincenzo Librandi_, Sep 14 2016 *) %o A223608 (PARI) for(n=1, 10^8, if(sigma(n)-2*n==-18, print1(n ", "))) %o A223608 (Magma) [n: n in [1..9*10^6] | (SumOfDivisors(n)-2*n) eq -18]; // _Vincenzo Librandi_, Sep 14 2016 %Y A223608 Cf. A000203, A033879, A223610 (abundance 18). %K A223608 nonn,more %O A223608 1,1 %A A223608 _Donovan Johnson_, Mar 23 2013 %E A223608 a(6) from _Giovanni Resta_, Mar 29 2013