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 A066971 #24 Dec 09 2024 23:23:25
%S A066971 1,7,8,15,28,56,24,60,24,56,56,120,60,168,168,63,56,120,96,252,104,
%T A066971 112,168,480,63,252,234,360,195,336,104,210,224,360,224,248,168,480,
%U A066971 360,546,252,728,224,504,480,336,224,504,186,255,336,260,360,1170,336,1170
%N A066971 a(n) = sigma(sigma(sigma(n))).
%C A066971 a(n) = A000203(A000203(A000203(n))) = A000203(A051027(n)) = A051027(A000203(n)). - _Jaroslav Krizek_, Jul 19 2009
%H A066971 Harry J. Smith, <a href="/A066971/b066971.txt">Table of n, a(n) for n = 1..1000</a>
%t A066971 lst={};Do[AppendTo[lst,DivisorSigma[1,DivisorSigma[1,DivisorSigma[1,n]]]],{n,5!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Mar 11 2009 *)
%t A066971 Table[Nest[DivisorSigma[1,#]&,n,3],{n,60}] (* _Harvey P. Dale_, Apr 06 2023 *)
%o A066971 (PARI) a(n) = { sigma(sigma(sigma(n))) } \\ _Harry J. Smith_, Apr 12 2010
%Y A066971 Cf. A000203, A051027.
%K A066971 nonn
%O A066971 1,2
%A A066971 _Benoit Cloitre_, Jan 26 2002