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 A333020 #10 Mar 06 2020 00:57:30 %S A333020 2,4,6,8,16,18,20,28,40,42,44,52,54,56,78,80,100,102,104,106,108,126, %T A333020 128,136,160,162,164,176,196,208,220,222,224,260,268,292,328,342,344, %U A333020 356,378,380,416,438,440,460,462,464,476,498,500,502,504,520,560,584 %N A333020 Starts of runs of 3 consecutive even numbers that are all totient numbers (A002202). %H A333020 Amiram Eldar, <a href="/A333020/b333020.txt">Table of n, a(n) for n = 1..10000</a> %H A333020 Wikipedia, <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function#Totient_numbers">Totient numbers</a>. %e A333020 2 is a term since 2, 4 and 6 are all totient numbers. %o A333020 (PARI) m = 3; v = vector(m); for(k=1, m, v[k] = istotient(2*k)); for(k = m+1, 300, if(Set(v) == [1], print1(2*(k-m),", ")); v = concat(v[2..m], istotient(2*k))) %Y A333020 Cf. A000010, A002202, A005277, A063512, A083533, A333019, A333021, A333022, A333023, A333024. %K A333020 nonn %O A333020 1,1 %A A333020 _Amiram Eldar_, Mar 05 2020