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 A138919 #19 Nov 11 2019 10:25:03
%S A138919 5,7,18,20,21,30,34,36,38,52,54,60,90,104,117,123,146,159,179,182,229,
%T A138919 278,388,405,410,439,552,557,735,806,807,1220,1272,1568,1688,1696,
%U A138919 1710,1814,2136,2262,2288,2862,3679,3814,4058,4304,4480,5070,5136,5154
%N A138919 Indices k such that A020510(k)=Phi[k](-11) is prime, where Phi is a cyclotomic polynomial.
%C A138919 Larger values are probable primes.
%H A138919 Robert Price, <a href="/A138919/b138919.txt">Table of n, a(n) for n = 1..91</a>
%H A138919 Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a>
%H A138919 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a>
%t A138919 Select[Range[1000], PrimeQ[Cyclotomic[#, -11]] &]
%o A138919 (PARI) for( i=1,999, ispseudoprime( polcyclo(i,-11)) & print1(",",i)) /* use ...subst(polcyclo(i),x,-11)... in PARI < 2.4.2 */
%Y A138919 Cf. A020510, A138920-A138940, A070518-A070527.
%K A138919 nonn
%O A138919 1,1
%A A138919 _M. F. Hasler_, Apr 04 2008
%E A138919 Edited by _T. D. Noe_, Oct 30 2008
%E A138919 a(32)-a(44) from _Robert Price_, Mar 16 2012
%E A138919 a(45)-a(50) from _Robert Price_, Apr 14 2012