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 A138933 #21 Sep 10 2024 16:14:13 %S A138933 1,3,6,7,9,10,12,13,14,15,21,24,26,33,36,40,46,60,63,70,71,72,86,103, %T A138933 108,130,132,143,145,154,161,236,255,261,276,279,287,304,364,430,464, %U A138933 513,528,541,562,665,672,680,707,718,747,760,782,828,875,892,974,984 %N A138933 Indices k such that A019321(k)=Phi[k](3) is prime, where Phi is a cyclotomic polynomial. %H A138933 Robert Price, <a href="/A138933/b138933.txt">Table of n, a(n) for n = 1..167</a> %H A138933 Yves Gallot, <a href="http://yves.gallot.pagesperso-orange.fr/papers/cyclotomic.html">Cyclotomic polynomials and prime numbers</a> %H A138933 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a> %t A138933 Select[Range[1000], PrimeQ[Cyclotomic[#, 3]] &] %o A138933 (PARI) for( i=1,999, ispseudoprime( polcyclo(i,3)) && print1( i",")) %Y A138933 Cf. A019321, A072226, A138920-A138940. %K A138933 nonn %O A138933 1,2 %A A138933 _M. F. Hasler_, Apr 03 2008