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 A049199 #14 Jul 13 2019 03:43:25 %S A049199 8,12,16,20,24,25,27,28,32,36,40,44,45,48,50,52,54,56,60,63,64,68,72, %T A049199 75,76,80,81,84,88,90,92,96,99,100,104,108,112,116,117,120,124,125, %U A049199 126,128,132,135,136,140,144,147,148,150,152,153,156,160,162,164,168,169 %N A049199 Nonsquarefree numbers whose Euler totient function is also nonsquarefree. %C A049199 Prime powers with sufficiently large exponents are in this sequence, including 8, 16, 32, 64, ..., 27, 81, ..., 25, 125. %H A049199 Amiram Eldar, <a href="/A049199/b049199.txt">Table of n, a(n) for n = 1..10000</a> %F A049199 k such that abs(mu(k)) = 0 and abs(mu(phi(k))) = 0. %e A049199 124 = 4*31 is in the sequence because phi(124)=60 and neither 124 nor 60 is squarefree. %t A049199 Select[Range[170], !SquareFreeQ[#] && !SquareFreeQ[EulerPhi[#]] &] (* _Amiram Eldar_, Jul 13 2019 *) %o A049199 (PARI) isok(n) = !issquarefree(n) && ! issquarefree(eulerphi(n)); \\ _Michel Marcus_, Jul 13 2019 %Y A049199 Cf. A000010, A005117, A013929, A049198. %K A049199 nonn %O A049199 1,1 %A A049199 _Labos Elemer_