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 A319314 #21 Sep 08 2022 08:46:23 %S A319314 1,3,4,5,6,8,10,12,384,640,768,896,960,24576,49152,950272,1425408, %T A319314 1572864,3145728,10485760,19398656,65011712,100663296,110057537, %U A319314 201326592,220115074,671088640,1879048192 %N A319314 Numbers k such that 2^phi(k) == phi(k)^2 (mod k^2). %C A319314 Sequence is infinite, i.e., 3*2^(3*(t-1)-(-1)^t) is a term for all t > 0. %C A319314 Prime terms (5, 110057537, ...) are in A246568 based on case A = +1. %o A319314 (PARI) isok(n) = Mod(2, n^2)^eulerphi(n)==eulerphi(n)^2; %o A319314 (Magma) [1] cat [n: n in [1..10^6] | 2^EulerPhi(n) mod n^2 eq EulerPhi(n)^2]; // _Vincenzo Librandi_, Sep 20 2018 %Y A319314 Cf. A077815, A077816, A246568, A292544. %K A319314 nonn,more %O A319314 1,2 %A A319314 _Altug Alkan_, Sep 17 2018