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 A217141 #12 Aug 22 2025 17:50:35
%S A217141 143,157,203,247,273,1147,1209,1679,2147,2279,2375,2445,2705,2747,
%T A217141 4331,4687,5049,6107,7367,7835,7869,7979,7991,9167,12127,17145,18501,
%U A217141 18753,18981,19803,22987,26733,27359,29097,29987,32829,35485,35763,37653,37851,39907
%N A217141 Numbers n such that phi(n) = phi(n+12) and n is not divisible by 2.
%H A217141 Donovan Johnson, <a href="/A217141/b217141.txt">Table of n, a(n) for n = 1..1000</a>
%t A217141 Select[Range[1,40000,2],EulerPhi[#]==EulerPhi[#+12]&] (* _Harvey P. Dale_, Aug 22 2025 *)
%o A217141 (PARI) {op=vector(N=12); Nd6=N/6;for( n=1, 1e4, if( op[n%N+1]+0==op[n%N+1]=eulerphi(n), if ((n-N) % Nd6 != 0, print1(n-N, ", "))))}
%Y A217141 Cf. A000010, A179188, A217139.
%K A217141 nonn
%O A217141 1,1
%A A217141 _Michel Marcus_, Sep 27 2012
%E A217141 Definition clarified by _Harvey P. Dale_, Aug 22 2025