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 A371241 #9 Mar 16 2024 05:22:15
%S A371241 1,1,2,4,6,4,12,6,8,16,10,22,20,12,16,40,42,20,42,20,24,52,66,32,24,
%T A371241 70,36,60,78,32,110,60,60,100,48,130,108,66,72,148,150,72,156,78,64,
%U A371241 132,100,168,160,102,210,104,106,168,228,88,112,232,96,238,240,110
%N A371241 Euler totient function applied to the zeroless numbers in base 3 (A032924).
%H A371241 Amiram Eldar, <a href="/A371241/b371241.txt">Table of n, a(n) for n = 1..10000</a>
%H A371241 William D. Banks and Igor E. Shparlinski, <a href="http://dx.doi.org/10.4064/aa112-4-1">Arithmetic properties of numbers with restricted digits</a>, Acta Arithmetica, Vol. 112, No. 4 (2004), pp. 313-332; <a href="https://eudml.org/doc/278042">alternative link</a>.
%F A371241 a(n) = A000010(A032924(n)).
%F A371241 Asymptotic mean of phi(k)/k over A032924: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k)/A032924(k) = 27/(4*Pi^2) = 1/A214549 = 0.683917... (Banks and Shparlinski, 2004).
%t A371241 EulerPhi[Select[Range[300], !MemberQ[IntegerDigits[#, 3], 0] &]]
%o A371241 (PARI) lista(kmax) = for(k = 1, kmax, if(vecmin(digits(k, 3)) > 0, print1(eulerphi(k), ", ")));
%Y A371241 Cf. A000010, A032924, A214549, A371239, A371240.
%K A371241 nonn,base,easy
%O A371241 1,3
%A A371241 _Amiram Eldar_, Mar 16 2024