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 A258644 #7 Aug 31 2015 21:05:48 %S A258644 0,0,0,0,4,0,0,0,80,0,0,0,176,0,1,32,368,0,1,0,112,0,0,0,240,0,16,27, %T A258644 368,0,0,0,752,5,0,80,272,0,1,176,220,0,0,0,608,80,1,0,1552,5,32,48, %U A258644 272,0,540,176,560,0,0,0,560,0,6,44,7168,7,0,0,284,12,0 %N A258644 Fourth arithmetic derivative of n. %H A258644 Alois P. Heinz, <a href="/A258644/b258644.txt">Table of n, a(n) for n = 0..10000</a> %F A258644 a(n) = A003415^4(n). %p A258644 d:= n-> n*add(i[2]/i[1], i=ifactors(n)[2]): %p A258644 A:= proc(n, k) option remember; `if`(k=0, n, d(A(n, k-1))) end: %p A258644 a:= n-> A(n, 4): %p A258644 seq(a(n), n=0..70); %Y A258644 Column k=4 of A258651. %Y A258644 Cf. A003415. %K A258644 nonn,look %O A258644 0,5 %A A258644 _Alois P. Heinz_, Jun 06 2015