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 A143868 #7 Jun 30 2015 13:21:30
%S A143868 8,84,815,7922,77250,759077,7492588,74198995,736401956,7319543972,
%T A143868 72834161468,725344237597
%N A143868 a(n)= Number of distinct prime divisors (taken together) of numbers of the form 2x^2-1 for x<=10^n.
%H A143868 Bernhard Helmes, <a href="http://www.devalco.de/quadr_Sieb_2x%5E2-1.php#4a">Prime sieving on the polynomial f(n)=2n^2-1</a>.
%t A143868 l = 0; p = 2; c = {}; a = {}; Do[k = p x^2 - 1; b = Divisors[k]; Do[If[PrimeQ[b[[n]]], AppendTo[a, b[[n]]]], {n, 1, Length[b]}]; If[N[Log[x]/Log[10]] == Round[N[Log[x]/Log[10]]], a = Union[a]; l = Length[a]; Print[l]; AppendTo[c, l]], {x, 1, 10000}]; c (*Artur Jasinski*)
%Y A143868 Cf. A143835.
%K A143868 nonn
%O A143868 1,1
%A A143868 _Artur Jasinski_, Sep 04 2008
%E A143868 Fixed broken link and corrected terms to agree with website - _Ray Chandler_, Jun 30 2015