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 A243983 #13 Jul 16 2014 06:29:56 %S A243983 0,0,4,6,0,4,0,6,4,0,0,16,0,0,9,6,0,4,0,6,4,0,0,24,0,0,4,6,0,9,0,6,4, %T A243983 0,12,16,0,0,4,24,0,4,0,6,9,0,0,24,0,0,4,6,0,4,0,6,4,0,0,43,0,0,20,6, %U A243983 0,4,0,6,4,12,0,24,0,0,9,6,0,4,0,24,4,0,0,42,0,0,4,6,0,9 %N A243983 Sum of twin divisors of n. %C A243983 See A243865 for definition of twin divisor. %H A243983 Jens Kruse Andersen, <a href="/A243983/b243983.txt">Table of n, a(n) for n = 1..10000</a> %F A243983 a(n) = A000203(n) - A243984(n). %e A243983 The positive divisors of 40 are 1, 2, 4, 5, 8, 10, 20, 40. Of these, 2, 4, 8, 10, are twin divisors. So a(40) = the sum of these divisors, which is 24. %Y A243983 Cf, A000203, A132748, A243865. %K A243983 nonn %O A243983 1,3 %A A243983 _Juri-Stepan Gerasimov_, Jun 16 2014