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 A086779 #18 Feb 24 2024 01:06:08
%S A086779 7,14,15,28,30,45,49,56,60,75,90,98,112,120,135,150,180,196,224,225,
%T A086779 240,270,300,343,360,375,392,405,448,450,480,540,600,675,686,720,750,
%U A086779 784,810,896,900,960,1080,1125,1200,1215,1350,1372,1440,1500,1568,1620
%N A086779 Numbers k such that k-th cyclotomic polynomial has exactly 7 nonzero terms.
%F A086779 {n: A051664(n)=7}. - _R. J. Mathar_, Sep 15 2012
%t A086779 Select[Range[2000], Count[CoefficientList[Cyclotomic[#, x], x], 0] == EulerPhi[#] - 6 &] (* _T. D. Noe_, Feb 13 2012 *)
%o A086779 (PARI) isok(n) = {my(p = polcyclo(n)); #select(x->x, vector(1+poldegree(p), k, polcoeff(p, k-1))) == 7;} \\ _Michel Marcus_, Oct 26 2017
%Y A086779 Cf. A086761.
%K A086779 nonn
%O A086779 1,1
%A A086779 Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 03 2003
%E A086779 Extended by _T. D. Noe_, Feb 13 2012