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 A078767 #5 Apr 11 2022 18:14:56 %S A078767 0,1,2,2,3,3,3,3,3,3,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, %T A078767 5,5,5,5,5,5,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, %U A078767 6,6,6,6,6,6,6,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 %N A078767 Let f(n) = A003434(n) be the number of iterations of phi needed to reach 1. Then a(n) = max(f(1), f(2), ..., f(n)). %o A078767 (PARI) epr(m,c)=if (c>0,m=eulerphi(m); c--; epr(m,c),m) x=1; for (n=1,100, while (epr(n,x)>1, x++); print1(x",")) %Y A078767 Cf. A003434. %K A078767 easy,nonn %O A078767 1,3 %A A078767 _Jon Perry_, Jan 09 2003 %E A078767 Description corrected by Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 31 2003