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 A086761 #31 Feb 23 2024 07:28:09 %S A086761 5,10,20,25,40,50,80,100,125,160,200,250,320,400,500,625,640,800,1000, %T A086761 1250,1280,1600,2000,2500,2560,3125,3200,4000,5000,5120,6250,6400, %U A086761 8000,10000,10240,12500,12800,15625,16000,20000,20480,25000,25600,31250,32000 %N A086761 Numbers k such that k-th cyclotomic polynomial has exactly 5 nonzero terms. %C A086761 A206787(a(n)) = 6. - _Reinhard Zumkeller_, Feb 12 2012 %C A086761 All terms have the form 2^a 5^b with a >= 0 and b > 0. - _T. D. Noe_, Feb 13 2012 %C A086761 If the above holds for all terms then this sequence is 5 * A003592. - _David A. Corneth_, Jul 04 2018 %t A086761 Select[Range[1000], Count[CoefficientList[Cyclotomic[#, x], x], 0] == EulerPhi[#] - 4 &] (* _T. D. Noe_, Feb 13 2012 *) %o A086761 (PARI) is(n) = v = Vec(polcyclo(n)); sum(i=1,#v,v[i]!=0) == 5 \\ _David A. Corneth_, Jul 04 2018 %Y A086761 Cf. A003592, A051664, A065119. %K A086761 nonn %O A086761 1,1 %A A086761 Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 02 2003 %E A086761 More terms from _T. D. Noe_, Feb 13 2012