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 A049195 #18 Mar 02 2021 05:59:37 %S A049195 5,8,10,12,13,15,16,17,19,20,21,24,25,26,27,28,29,30,32,33,34,35,36, %T A049195 37,38,39,40,41,42,44,45,48,50,51,52,53,54,55,56,57,58,60,61,63,64,65, %U A049195 66,68,69,70,72,73,74,75,76,77,78,80,81,82,84,85,87,88,89,90,91,92,93,95 %N A049195 Numbers k such that the Euler totient function phi(k) is divisible by a square. %C A049195 For k > 2 and p a prime: p^k is in this sequence. - _Enrique Pérez Herrero_, Apr 25 2013 %C A049195 The asymptotic density of this sequence is 1 since its complement (A049149) has a density 0. - _Amiram Eldar_, Mar 02 2021 %H A049195 Enrique Pérez Herrero, <a href="/A049195/b049195.txt">Table of n, a(n) for n = 1..2500</a> %e A049195 72 and 73 belong because neither phi(72) = 24 nor phi(73) = 72 are squarefree. %t A049195 Select[Range[100], MoebiusMu[EulerPhi[#]] == 0 &] %t A049195 Select[Range[100],!SquareFreeQ[EulerPhi[#]]&] (* _Harvey P. Dale_, Apr 30 2018 *) %Y A049195 Complement of A049149. %Y A049195 Cf. A000010, A005117, A013929. %K A049195 nonn %O A049195 1,1 %A A049195 _Labos Elemer_