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 A096991 #3 Oct 15 2013 22:32:33 %S A096991 401,451,489,491,505,513,567,577,629,631,652,661,673,679,685,691,713, %T A096991 731,737,751,757,769,773,791,802,808,811,817,825,829,833,847,851,853, %U A096991 859,867,869,871,873,877,889,893,899,901,902,907,911,917,919,923,931 %N A096991 Initial values for f(x)=sigma(phi[x])=A062402[x] such that iteration of f ends in cycle of length=4. %Y A096991 Cf. A062402, A096926. %K A096991 nonn %O A096991 1,1 %A A096991 _Labos Elemer_, Jul 19 2004