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 A319481 #5 Sep 20 2018 08:17:15 %S A319481 1,2,6,12,168,240,14880,65280,4294901760,7608944640,1125874137169920, %T A319481 18446744069414584320 %N A319481 Integers k such that uphi(k) divides k, where uphi is the unitary phi function (A047994). %H A319481 Tomohiro Yamada, <a href="https://arxiv.org/abs/1806.00647">An analog of perfect numbers involving the unitary totient function</a>, arXiv:1806.00647 [math.NT], 2018. See (2) on p. 2. %o A319481 (PARI) uphi(n) = my(f=factor(n)~); prod(i=1, #f, f[1, i]^f[2, i]-1); %o A319481 isok(n) = frac(n/uphi(n)) == 0; %Y A319481 Cf. A047994. %Y A319481 A030163 is a subsequence. %K A319481 nonn,more %O A319481 1,2 %A A319481 _Michel Marcus_, Sep 20 2018