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 A258857 #4 Jun 12 2015 20:46:07 %S A258857 0,0,0,0,4,0,4,4,2304,2304,0,0,12288,4,80,208,81920,4,208,512,81920, %T A258857 80,32,512,16092,512,208,138240,30848,0,2304,0,622592,512,0,4,3000, %U A258857 2304,4,30848,3000,4,16,32,114752,2160,4,80,772352,936,208,332,52056,12288 %N A258857 Seventh pi-based arithmetic derivative of n. %H A258857 Alois P. Heinz, <a href="/A258857/b258857.txt">Table of n, a(n) for n = 0..10000</a> %F A258857 a(n) = A258851^7(n). %p A258857 with(numtheory): %p A258857 d:= n-> n*add(i[2]*pi(i[1])/i[1], i=ifactors(n)[2]): %p A258857 A:= proc(n, k) option remember; `if`(k=0, n, d(A(n, k-1))) end: %p A258857 a:= n-> A(n, 7): %p A258857 seq(a(n), n=0..100); %Y A258857 Column k=7 of A258850. %Y A258857 Cf. A000720, A258851. %K A258857 nonn %O A258857 0,5 %A A258857 _Alois P. Heinz_, Jun 12 2015