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 A358489 #22 Dec 21 2022 21:24:19 %S A358489 6227180929,6227182993,6227186509,6227199361,6227220691,6227229637, %T A358489 6227245393,6227246107,6227260969,6227267713,6227268799,6227279341, %U A358489 6227280491,6227288461,6227311397,6227314111,6227327761,6227351861,6227355097,6227376241,6227447761,6227454979 %N A358489 Numbers k such that phi(k) = 13! where phi is the Euler totient function (A000010). %C A358489 A055487(13) = 6227180929 is the first term in the sequence. %C A358489 A165774(13) = 37020293310 is the last term in the sequence. %H A358489 Project Euler, <a href="https://projecteuler.net/problem=248">Problem 248. Numbers for which Euler's totient function equals 13!</a>. %o A358489 (Python) %o A358489 from sympy import totient %o A358489 def isok(k): return totient(k) == 6227020800 %Y A358489 Cf. A000010, A055487, A165774. %K A358489 nonn,fini %O A358489 1,1 %A A358489 _Darío Clavijo_, Nov 18 2022