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 A138936 #13 Nov 11 2019 10:26:35 %S A138936 1,2,3,4,6,7,8,18,21,22,24,29,30,42,50,62,71,86,90,94,118,124,127,144, %T A138936 154,192,214,271,354,360,411,480,509,558,575,663,764,814,825,874,1028, %U A138936 1049,1050,1102,1113,1131,1158,1376,1464,1468,1535,1622,1782,1834 %N A138936 Indices n such that A019324(k)=Phi[k](6) is prime, where Phi is a cyclotomic polynomial. %H A138936 Robert Price, <a href="/A138936/b138936.txt">Table of n, a(n) for n = 1..103</a> %H A138936 Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a> %H A138936 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a> %t A138936 Select[Range[1000], PrimeQ[Cyclotomic[#, 6]] &] %o A138936 (PARI) for( i=1,999, ispseudoprime( polcyclo(i,6)) && print1( i",")) /* use ...subst(polcyclo(i),x,6)... in PARI < 2.4.2 */ %Y A138936 Cf. A019324, A138920-A138940. %K A138936 nonn %O A138936 1,2 %A A138936 _M. F. Hasler_, Apr 03 2008 %E A138936 a(41)-a(54) from _Robert Price_, Apr 16 2012