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 A070025 #23 Sep 24 2024 09:22:29
%S A070025 6,150,2730,9000,9240,35280,41760,43050,53280,65520,76650,96180,
%T A070025 111030,148200,197370,207480,213360,226380,254280,264600,309480,
%U A070025 332160,342450,352740,375450,381990,440550,458790,501030,527070,552030,642360,660810
%N A070025 At these values of k, the 1st, 2nd, 3rd and 4th cyclotomic polynomials all give prime numbers.
%C A070025 Numbers k such that k-1, k+1, k^2+k+1 and k^2+1 are all primes.
%H A070025 Amiram Eldar, <a href="/A070025/b070025.txt">Table of n, a(n) for n = 1..10000</a>
%e A070025 For k = 6: 5, 7, 43 and 37 are prime values of the first 4 cyclotomic polynomials.
%t A070025 lst={};Do[If[PrimeQ[n-1]&&PrimeQ[n+1]&&PrimeQ[1+n+n^2]&&PrimeQ[1+n^2], AppendTo[lst, n]], {n, 10^6}];lst (* _Vladimir Joseph Stephan Orlovsky_, Aug 19 2008 *)
%t A070025 Select[Range[10^6], Function[k, AllTrue[Cyclotomic[#, k] & /@ Range@ 4, PrimeQ]]] (* _Michael De Vlieger_, Jul 18 2017 *)
%o A070025 (PARI) is(k) = isprime(k-1) && isprime(k+1) && isprime(k^2+1) && isprime(k^2+k+1); \\ _Amiram Eldar_, Sep 24 2024
%Y A070025 Cf. A070155, A070156, A070157, A000068, A006313, A006314, A006315, A006316, A056993, A056994, A056995, A005574, A057465, A057002, A070020, A070042.
%K A070025 easy,nonn
%O A070025 1,1
%A A070025 _Labos Elemer_, May 07 2002