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 A078553 #11 Aug 01 2019 11:32:36 %S A078553 17,41,13,313,41,1201,257,73,313,7321,41,14281,1201,313,41,41761,73, %T A078553 3833,313,1201,7321,139921,257,601,14281,193,1201,353641,313,1129,241, %U A078553 7321,41761,1201,73,10529,3833,14281,313,10313,1201,521,7321,313 %N A078553 Largest prime dividing sigma(4,n). %H A078553 Amiram Eldar, <a href="/A078553/b078553.txt">Table of n, a(n) for n = 2..10000</a> %F A078553 a(n) = A006530(A001159(n)). %e A078553 Observe nontrivial frequent occurrence of several primes like 73,313,14281, etc. %t A078553 gpf[n_] := FactorInteger[n][[-1, 1]]; a[n_] := gpf[DivisorSigma[4, n]]; Array[a, 50, 2] (* _Amiram Eldar_, Aug 01 2019 *) %Y A078553 Cf. A006530, A001157-A001160, A071190. %K A078553 nonn %O A078553 2,1 %A A078553 _Labos Elemer_, Dec 05 2002