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 A152940 #6 Nov 05 2017 13:18:37 %S A152940 105,165,195,255,273,285,345,357,429,455,555,561,609,615,627,645,705, %T A152940 715,759,777,795,805,897,957,969,987,1001,1005,1015,1023,1045,1065, %U A152940 1085,1095,1105,1131,1185,1221,1239,1245,1265,1295,1407,1419,1435,1455,1491 %N A152940 Odd squarefree numbers n such that the cyclotomic polynomial Phi(n,x) has height 2. %C A152940 The height of a polynomial is the maximum of the absolute value of its coefficients. Subsequence of A154430. %H A152940 T. D. Noe, <a href="/A152940/b152940.txt">Table of n, a(n) for n = 1..1000</a> %o A152940 (PARI) is(n)=issquarefree(n) && n%2 && vecmax(abs(Vec(polcyclo(n))))==2 \\ _Charles R Greathouse IV_, Nov 05 2017 %Y A152940 Cf. A152955, A152941, A152942, A152943. %K A152940 nonn %O A152940 1,1 %A A152940 _T. D. Noe_, Dec 16 2008, Jan 09 2009