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 A258853 #9 Aug 31 2015 21:08:23 %S A258853 0,0,0,0,4,1,4,4,32,32,3,2,80,4,8,12,208,4,12,20,208,30,25,20,108,16, %T A258853 53,351,192,5,32,3,512,20,5,6,248,32,13,192,248,7,26,19,704,172,6,8, %U A258853 1600,156,71,49,324,80,864,56,332,16,116,4,536,37,32,424,2432 %N A258853 Third pi-based arithmetic derivative of n. %H A258853 Alois P. Heinz, <a href="/A258853/b258853.txt">Table of n, a(n) for n = 0..10000</a> %F A258853 a(n) = A258851^3(n). %F A258853 a(A258995(n)) = n. %p A258853 with(numtheory): %p A258853 d:= n-> n*add(i[2]*pi(i[1])/i[1], i=ifactors(n)[2]): %p A258853 A:= proc(n, k) option remember; `if`(k=0, n, d(A(n, k-1))) end: %p A258853 a:= n-> A(n, 3): %p A258853 seq(a(n), n=0..100); %Y A258853 Column k=3 of A258850. %Y A258853 Cf. A000720, A258851, A258995. %K A258853 nonn,look %O A258853 0,5 %A A258853 _Alois P. Heinz_, Jun 12 2015