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 A090553 #9 Dec 05 2013 19:56:38
%S A090553 1,3,6,12,12,24,24,24,72,72,72,72,144,144,144,144,144,288,288,288,576,
%T A090553 576,576,576,576,576,576,576,1152,1152,1152,1152,1152,1152,1152,2304,
%U A090553 2304,2304,2304,2304,2304,2304,2304,2304,2304,2304,2304,2304,4608,4608
%N A090553 Sigma(A090552(n)).
%F A090553 a(n) = A000203(A090552(n)). - _Michel Marcus_, Oct 12 2013
%o A090553 (PARI) lista(nn) = {a = 1; print1(a, ", "); for (n = 1, nn, sa = sigma(a); a++; while (sigma(a) % sa, a++); print1(sigma(a), ", "););} \\ _Michel Marcus_, Oct 12 2013
%Y A090553 Cf. A007368, A090552.
%K A090553 nonn
%O A090553 1,2
%A A090553 _Amarnath Murthy_, Dec 09 2003
%E A090553 Corrected and extended by _David Wasserman_, Jan 04 2006