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 A227429 #15 Nov 28 2021 11:50:37
%S A227429 1,3,4,12,21,39,91,156,381,1668,3292,4541,6515,12927,49492,72412,
%T A227429 100595,158708
%N A227429 Numbers k such that Sum_{j=1..k} j^phi(j) == 0 (mod k).
%C A227429 a(17) > 10^5. - _Giovanni Resta_, Jul 11 2013
%C A227429 a(19) > 2473000. - _Kevin P. Thompson_, Nov 28 2021
%e A227429 4 is a member of the sequence since Sum_{j=1..4} j^phi(j) = 1^phi(1) + 2^phi(2) + 3^phi(3) + 4^phi(4) = 1^1 + 2^1 + 3^2 + 4^2 = 28 which is divisible by 4.
%p A227429 with(numtheory); ListA227429:=proc(q) local i,n;
%p A227429 for n from 1 to q do if add(i^phi(i),i=1..n) mod n=0 then print(n);
%p A227429 fi; od; end: ListA227429(10^6);
%Y A227429 Cf. A000010, A227427.
%K A227429 nonn,more
%O A227429 1,2
%A A227429 _Paolo P. Lava_, Jul 11 2013
%E A227429 a(10)-a(16) from _Giovanni Resta_, Jul 11 2013
%E A227429 a(17)-a(18) from _Kevin P. Thompson_, Nov 28 2021