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 A055201 #25 Mar 01 2020 05:42:30
%S A055201 1,2,3,4,5,6,7,8,9,11,12,13,15,17,18,22,23,24,29,36,37,40,53,55,59,60,
%T A055201 61,62,63,68,69,74,83,86,93,97,107,109,115,116,117,118,123,128,129,
%U A055201 139,142,147,153,154,157,158,162,167,170,175,179,181,182,183,193,194,196
%N A055201 Numbers k such that A005728(k) is prime.
%C A055201 From a question by Leo Moser.
%D A055201 Martin Gardner, "The Last Recreations," Chapter entitled "Strong Laws of Small Primes," Copernicus, Springer-Verlag, NY, 1997, page 199.
%H A055201 Amiram Eldar, <a href="/A055201/b055201.txt">Table of n, a(n) for n = 1..10000</a>
%H A055201 Leo Moser, <a href="https://books.google.com/books?id=u6N0yfe69RcC&pg=PA312">Problem P42</a>, Canadian Mathematical Bulletin, Vol. 5, No. 3 (1962), pp. 312-313.
%t A055201 s=1; Do[s = s + EulerPhi[n]; If[PrimeQ[s], Print[n]], {n, 200}]
%Y A055201 Cf. A005728.
%Y A055201 Complement of A055197.
%K A055201 easy,nonn
%O A055201 1,2
%A A055201 _Robert G. Wilson v_, Jul 04 2000