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 A258357 #7 Jun 20 2015 14:43:23 %S A258357 0,1,2,3,13,470,2957 %N A258357 Numbers n such that cyclotomic polynomial value Phi(7,n!) is prime. %C A258357 Except for the values 0,1,2 and 3, terms correspond to probable primes. %C A258357 a(8) > 6502. %C A258357 Also, numbers n such that n! belongs to A100330. - _Michel Marcus_, May 30 2015 %e A258357 3 is in the sequence because Phi(7,3!) = 1 + 6 + 6^2 + 6^3 + 6^4 + 6^5 + 6^6 = 55987 is prime. %t A258357 Select[Range[0, 6502], PrimeQ[Cyclotomic[7, #!]] &] %Y A258357 Cf. A002981, A002982, A046029, A200906. %K A258357 nonn,more %O A258357 1,3 %A A258357 _Robert Price_, May 27 2015