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 A070042 #16 Sep 24 2024 09:26:00
%S A070042 1068630,1441590,1867950,3429300,4084230,5651730,6322890,6770610,
%T A070042 7158630,7804830,9437760,9624270,13625850,23194860,25848840,26588520,
%U A070042 28714950,29451840,32984430,33650580,36500910,38177130,42856590,49531020,50016540,50222070,52083330,54637590
%N A070042 At these values of k the 1st, 2nd, 3rd, 4th and 5th cyclotomic polynomials all give prime numbers.
%C A070042 Numbers k such that C1(k) = k-1, C2(k) = k+1, C3(k) = k^2+k+1, C4(k) = k^2+1 and C5(k) = k^4+k^3+k^2+k+1 are all primes.
%H A070042 Amiram Eldar, <a href="/A070042/b070042.txt">Table of n, a(n) for n = 1..10000</a>
%e A070042 For k = 1068630: the 1st, 2nd, 3rd, 4th and 5th cyclotomic polynomials give a quintet of primes: {1068629, 1068631, 1141971145531, 1141970076901, 1304096876879617162402531}.
%o A070042 (PARI) is(k) = isprime(k-1) && isprime(k+1) && isprime(k^2+1) && isprime(k^2+k+1) && isprime(k^4+k^3+k^2+k+1) ; \\ _Amiram Eldar_, Sep 24 2024
%Y A070042 Cf. A070155, A070156, A070157, A000068, A006313, A006314, A006315, A006316, A056993, A056994, A056995, A005574, A057465, A057002, A070020, A070025.
%K A070042 easy,nonn
%O A070042 1,1
%A A070042 _Labos Elemer_, May 07 2002
%E A070042 More terms from _Don Reble_, May 11 2002
%E A070042 a(24)-a(28) from _Amiram Eldar_, Sep 24 2024