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 A305828 #10 Jun 10 2018 20:22:39 %S A305828 8,9,25,58,89,158,307,571,282,466,1303,1043,913,1384,1977,1486,3308, %T A305828 2936,3497,3983,2930,4426,2338,3401,4668,6070,6186,6430,10910,4994, %U A305828 9671,4997,9053,10583,13123,10874,22611,14366,30066,8328,10031,15206,11873,17006 %N A305828 The n-th number m such that a nontrivial prime(n)-th root of unity modulo m exists. %C A305828 For n > 1 the n-th number m such that phi(m) is divisible by the n-th prime. %H A305828 Alois P. Heinz, <a href="/A305828/b305828.txt">Table of n, a(n) for n = 1..740</a> %F A305828 a(n) = A277915(n,n). %Y A305828 Main diagonal of A277915. %Y A305828 Cf. A000010, A000040. %K A305828 nonn %O A305828 1,1 %A A305828 _Alois P. Heinz_, Jun 10 2018