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 A124490 #13 Oct 11 2019 11:07:08
%S A124490 1447110,2623005,4095000,4339335,6975780,9080190,12382755,19455975,
%T A124490 20322960,30020760,32261985,54202995,62014155,63196350,66383520,
%U A124490 71369340,94571295,121012185,124225920,162780660,177109380,196068180,223888665,303047745,310143960
%N A124490 Numbers n such that 2n-1, 4n-1, 6n-1, 8n-1, 10n-1, 12n-1 and 14n-1 are primes.
%t A124490 Select[3*5*7*Range[2000000], And @@ PrimeQ /@ ({2, 4, 6, 8, 10, 12, 14}*# - 1) &] (* _Ray Chandler_, Nov 21 2006 *)
%t A124490 pr7Q[n_]:=AllTrue[2*Range[7]n-1,PrimeQ]; Select[105*Range[3*10^6],pr7Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, May 17 2018 *)
%Y A124490 Cf. A124485-A124492.
%K A124490 nonn
%O A124490 1,1
%A A124490 _Artur Jasinski_, Nov 04 2006
%E A124490 Extended by _Ray Chandler_, Nov 21 2006
%E A124490 More terms from _Harvey P. Dale_, May 17 2018