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 A331273 #25 Apr 11 2020 10:29:36 %S A331273 0,1,1,1,1,1,1,3,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,3,1,1,3,1,1,1,1,5,1,1, %T A331273 1,1,1,1,1,3,1,1,1,1,1,1,1,3,1,1,1,1,1,3,1,3,1,1,1,1,1,1,1,3,1,1,1,1, %U A331273 1,1,1,3,1,1,1,1,1,1,1,3,3,1,1,1,1,1,1 %N A331273 Sum of the iterated exponential totient function (A072911). %C A331273 Analogous to A092693 with the exponential totient function ephi instead of the Euler totient function phi (A000010). %C A331273 a(n) = 1 for n > 1 which is cubefree (A004709) and a(n) > 1 for n in A046099. %H A331273 Amiram Eldar, <a href="/A331273/b331273.txt">Table of n, a(n) for n = 1..10000</a> %e A331273 a(8) = ephi(8) + ephi(ephi(8)) = 2 + 1 = 3 (where ephi is A072911). %t A331273 ephi[n_] := Times @@ EulerPhi[FactorInteger[n][[;; , 2]]]; s[n_] := Plus @@ FixedPointList[ephi, n] - n - 1; Array[s, 100] %Y A331273 Cf. A004709, A046099, A072911, A092693. %K A331273 nonn %O A331273 1,8 %A A331273 _Amiram Eldar_, Feb 25 2020