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 A138925 #17 Nov 11 2019 10:25:32 %S A138925 5,6,12,14,22,24,26,28,45,48,55,56,67,88,92,94,98,99,101,103,108,114, %T A138925 116,120,229,236,248,254,265,282,288,298,322,347,362,384,399,420,500, %U A138925 536,567,615,620,714,835,992,1047,1064,1238,1794,1858,1962,2313,2397 %N A138925 Indices k such that A020504(k)=Phi[k](-5) is prime, where Phi is a cyclotomic polynomial. %H A138925 Robert Price, <a href="/A138925/b138925.txt">Table of n, a(n) for n = 1..114</a> %H A138925 Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a> %t A138925 Select[ Range[ 2000], PrimeQ[ Cyclotomic[#, -5]] &] (* _Robert G. Wilson v_, Mar 25 2012 *) %o A138925 (PARI) for( i=1,999, ispseudoprime( polcyclo(i,-5)) && print1( i",")) /* use ...subst(polcyclo(i),x,-5)... in PARI < 2.4.2 */ %Y A138925 Cf. A020504, A138920-A138940. %K A138925 nonn %O A138925 1,1 %A A138925 _M. F. Hasler_, Apr 03 2008 %E A138925 a(53)-a(54) from _Robert Price_, Apr 05 2012