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 A333019 #15 Mar 06 2020 00:57:33 %S A333019 2,4,6,8,10,16,18,20,22,28,30,40,42,44,46,52,54,56,58,64,70,78,80,82, %T A333019 100,102,104,106,108,110,126,128,130,136,138,148,160,162,164,166,176, %U A333019 178,190,196,198,208,210,220,222,224,226,238,250,260,262,268,270,280 %N A333019 Numbers k such that both k and k + 2 are totient numbers (A002202). %H A333019 Amiram Eldar, <a href="/A333019/b333019.txt">Table of n, a(n) for n = 1..10000</a> %H A333019 Wikipedia, <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function#Totient_numbers">Totient numbers</a>. %e A333019 2 is a term since both 2 and 4 are totient numbers. %o A333019 (PARI) for(k = 1, 150, if(istotient(2*k) && istotient(2*k+2), print1(2*k,", "))) %Y A333019 Cf. A000010, A002202, A005277, A063512, A083533, A333020, A333021, A333022, A333023, A333024. %K A333019 nonn %O A333019 1,1 %A A333019 _Amiram Eldar_, Mar 05 2020