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 A124492 #13 Apr 20 2019 06:15:18
%S A124492 2,2,2,3,3,77385,1447110,1447110,203937090,107290072890,4724240531010,
%T A124492 123618251967210,1272603355923900,9089306184994125090
%N A124492 a(n) = least k such that 2*i*k - 1 is prime for 1 <= i <= n.
%t A124492 a[n_] := Block[{k = If[n < 6, 1, 5], s}, s = k; While[! AllTrue[k 2 Range[n] - 1, PrimeQ], k += s]; k]; Array[a, 8] (* _Giovanni Resta_, Apr 01 2017 *)
%Y A124492 Cf. A006254, A124485-A124491, A071576.
%K A124492 nonn,more
%O A124492 1,1
%A A124492 _Artur Jasinski_, Nov 04 2006
%E A124492 Corrected and extended by _Don Reble_, Nov 05 2006
%E A124492 a(12)-a(14) from _Giovanni Resta_, Apr 01 2017