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 A117318 #16 Nov 09 2021 02:57:02 %S A117318 431985,757335,865365,1134915,1296885,1297815,1675365,1729335,1891815, %T A117318 2161785,2162715,2595165,2648715,2649585,3027165,3028035,3132015, %U A117318 3133785,3347985,3405615,3565785,3784065,3891585,4698465,4920285,5188935,5189865,5676315 %N A117318 Numbers n such that Phi(n,x) is a flat cyclotomic polynomial of order four. %C A117318 A flat polynomial is defined to be a polynomial whose coefficients are -1, 0, or 1. Order four means that n is the product of four odd primes p<q<r<s. %C A117318 For pqrs to be flat, it appears that three conditions on p < q < r < s are required: q = -1 (mod p), r = +-1 (mod pq), and s = +-1 (mod pqr). [_T. D. Noe_, Apr 13 2010] %H A117318 T. D. Noe, <a href="/A117318/b117318.txt">Table of n, a(n) for n=1..216</a> %H A117318 Nathan Kaplan, <a href="http://www.emis.de/journals/INTEGERS/papers/k30/k30.Abstract.html">Flat cyclotomic polynomials of order four and higher</a>, #A30, Integers 10 (2010), 357-363. %H A117318 Carlo Sanna, <a href="https://arxiv.org/abs/2111.04034">A Survey on Coefficients of Cyclotomic Polynomials</a>, arXiv:2111.04034 [math.NT], 2021. %Y A117318 Cf. A117223 (third-order flat cyclotomic polynomials). %K A117318 nonn %O A117318 1,1 %A A117318 _T. D. Noe_, Mar 07 2006