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 A053569 #14 Jun 15 2024 05:48:39
%S A053569 3,6,13,18,12,31,18,20,32,36,24,31,42,40,30,48,54,48,38,42,44,78,72,
%T A053569 48,57,93,72,98,54,72,90,60,62,127,84,144,68,96,144,72,74,124,140,96,
%U A053569 80,121,126,84,108,132,120,180,90,168,144,120,98,156,217,102,104,192,162
%N A053569 Sum of divisors of numbers which cannot be sum of divisors of any number.
%C A053569 See also comments in A053474.
%H A053569 Amiram Eldar, <a href="/A053569/b053569.txt">Table of n, a(n) for n = 1..10000</a>
%F A053569 a(n) = A000203(A007369(n)).
%e A053569 The 13th non-sigma number is 26. Its divisors are {26,13,2,1} of which the sum is 42. So a(13) = 42.
%e A053569 Also a(20) = 42, the divisor sum of 20th term in A007369, which is 41.
%Y A053569 Cf. A000203, A007369, A053474.
%K A053569 nonn
%O A053569 1,1
%A A053569 _Labos Elemer_, Jan 17 2000