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 A223607 #20 Sep 08 2022 08:46:04 %S A223607 46,154,190,2656,6490,44650,318250,1360810,1503370,1788490,3214090, %T A223607 103712410,3915380170,6077111050,9796360330,10828121356, %U A223607 33086522327050,35966517350410,11577093570201610,16726040141635450,576460762503970816 %N A223607 Numbers n whose deficiency is 20: sigma(n) - 2*n = -20. %C A223607 Suggested by _N. J. A. Sloane_ and _Robert G. Wilson v_. %C A223607 a(17) > 10^12. %C A223607 a(17) > 10^13. - _Giovanni Resta_, Mar 29 2013 %C A223607 a(22) > 10^18. - _Hiroaki Yamanouchi_, Aug 21 2018 %C A223607 Any term x of this sequence can be combined with any term y of A223611 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 A223607 n = 1360810. sigma(n)-2*n = -20. %t A223607 Select[Range[1, 10^8], DivisorSigma[1, #] - 2 # == - 20 &] (* _Vincenzo Librandi_, Sep 14 2016 *) %o A223607 (PARI) for(n=1, 10^8, if(sigma(n)-2*n==-20, print1(n ", "))) %o A223607 (Magma) [n: n in [1..9*10^6] | (SumOfDivisors(n)-2*n) eq -20]; // _Vincenzo Librandi_, Sep 14 2016 %Y A223607 Cf. A000203, A033879, A223611 (abundance 20). %K A223607 nonn,more %O A223607 1,1 %A A223607 _Donovan Johnson_, Mar 23 2013 %E A223607 a(17)-a(21) from _Hiroaki Yamanouchi_, Aug 21 2018