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 A138922 #12 Nov 11 2019 13:47:38 %S A138922 6,15,18,21,39,69,159,165,174,231,378,408,501,504,606,873,897,1122, %T A138922 1209,1395,1947,2040,2361,2778,3369,7305,7647,8154,8331,9483,13071, %U A138922 14616,15819,20301,21282,27144,31083,34725,35775,36855,38118,39360 %N A138922 Indices k such that A020507(k)=Phi[k](-8) is prime, where Phi is a cyclotomic polynomial. %H A138922 Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a> %t A138922 Select[Range[1000], PrimeQ[Cyclotomic[#, -8]] &] %o A138922 (PARI) for( i=1,999, ispseudoprime( polcyclo(i,-8)) && print1( i",")) /* use ...subst(polcyclo(i),x,-8)... in PARI < 2.4.2 */ %Y A138922 Cf. A020507, A138920-A138940. %K A138922 nonn,more %O A138922 1,1 %A A138922 _M. F. Hasler_, Apr 03 2008 %E A138922 a(18)-a(42) from _Robert Price_, Mar 25 2012