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 A125839 #8 Apr 01 2017 06:02:28
%S A125839 1,1,6,18,120,1260,1485540,28667100,28667100,842889105240,
%T A125839 2281585556250,163881570370980,45187548280664790
%N A125839 a(n) is the smallest number m such that k*m - 1 is prime for all k=3,4,...,n.
%C A125839 For n > 6, 10 divides a(n).
%H A125839 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_379.htm">Problems & puzzles</a>.
%e A125839 a(11)=28667100 because 3*28667100-1, 4*28667100-1, 5*28667100-1, 6*28667100-1, 7*28667100-1, 8*28667100-1, 9*28667100-1, 10*28667100-1 & 11*28667100-1 are prime and 28667100 is the smallest number with this property.
%t A125839 a[n_] := Block[{k = If[n<5, 1, 6], s}, s = k; While[! AllTrue[k Range[3, n] - 1, PrimeQ], k += s]; k]; a /@ Range[3, 9] (* _Giovanni Resta_, Mar 29 2017 *)
%Y A125839 Cf. A125838, A088651, A088250.
%K A125839 hard,more,nonn
%O A125839 3,3
%A A125839 Luke Pebody (luke.pebody(AT)gmail.com), Jan 02 2007
%E A125839 a(12)-a(13) from _Farideh Firoozbakht_
%E A125839 a(14)-a(15) from _Giovanni Resta_, Mar 30 2017