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 A138927 #24 Sep 10 2024 16:14:30 %S A138927 3,5,6,7,12,13,14,18,23,24,26,30,35,36,40,42,43,60,65,66,72,77,108, %T A138927 126,132,142,206,215,236,276,281,286,290,304,322,359,364,391,464,487, %U A138927 510,522,528,529,535,558,574,577,672,680,713,731,760,799,828,892,984 %N A138927 Indices k such that A020502(k)=Phi[k](-3) is prime, where Phi is a cyclotomic polynomial. %H A138927 Robert Price, <a href="/A138927/b138927.txt">Table of n, a(n) for n = 1..157</a> %H A138927 Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a> %H A138927 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a> %t A138927 Select[ Range[3, 1000], PrimeQ[ Cyclotomic[#, -3]] &] (* _Robert G. Wilson v_, Mar 25 2012 *) %o A138927 (PARI) for( i=1,999, ispseudoprime( polcyclo(i,-3)) && print1( i",")) %Y A138927 Cf. A020502, A138920-A138940. %K A138927 nonn %O A138927 1,1 %A A138927 _M. F. Hasler_, Apr 03 2008