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 A258854 #4 Jun 12 2015 20:44:17 %S A258854 0,0,0,0,4,0,4,4,80,80,2,1,208,4,12,20,512,4,20,32,512,53,30,32,324, %T A258854 32,16,864,704,3,80,2,2304,32,3,7,460,80,6,704,460,4,25,8,2432,228,7, %U A258854 12,6720,332,20,56,1188,208,3888,116,424,32,156,4,956,12,80,764 %N A258854 Fourth pi-based arithmetic derivative of n. %H A258854 Alois P. Heinz, <a href="/A258854/b258854.txt">Table of n, a(n) for n = 0..10000</a> %F A258854 a(n) = A258851^4(n). %p A258854 with(numtheory): %p A258854 d:= n-> n*add(i[2]*pi(i[1])/i[1], i=ifactors(n)[2]): %p A258854 A:= proc(n, k) option remember; `if`(k=0, n, d(A(n, k-1))) end: %p A258854 a:= n-> A(n, 4): %p A258854 seq(a(n), n=0..100); %Y A258854 Column k=4 of A258850. %Y A258854 Cf. A000720, A258851. %K A258854 nonn %O A258854 0,5 %A A258854 _Alois P. Heinz_, Jun 12 2015