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 A064281 #9 Sep 03 2024 19:50:01
%S A064281 4,1,1,13,676,283,14311,12022,27346,14965,3427,100942,12370,1237,3274,
%T A064281 42382,18619,4570,457,434869,203362,305491,213742,436831,217198,
%U A064281 168586,258214,215737,1312441,272848,744082,2059111,351055,712333,1880302
%N A064281 Least k such that k*10^n+1, k*10^n+3, k*10^n+7 and k*10^n+9 are all prime.
%H A064281 Sean A. Irvine, <a href="/A064281/b064281.txt">Table of n, a(n) for n = 0..50</a>
%t A064281 Do[k = 1; While[ !PrimeQ[k*10^n + 1] || !PrimeQ[k*10^n + 3] || !PrimeQ[k*10^n + 7] || !PrimeQ[k*10^n + 9], k++ ]; Print[k], {n, 0, 20} ]
%t A064281 lk[n_]:=Module[{k=1},While[!AllTrue[k*10^n+{1,3,7,9},PrimeQ],k++];k]; Array[lk,40,0] (* _Harvey P. Dale_, Sep 03 2024 *)
%K A064281 nonn
%O A064281 0,1
%A A064281 _Robert G. Wilson v_, Oct 14 2001