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 A139421 #8 Feb 15 2014 20:39:42
%S A139421 1,2,3,2,5,3,7,3,7,5,11,5,13,7,13,7,17,7,19,7,19,11,23,11,23,13,23,13,
%T A139421 29,13,31,13,31,17,31,17,37,19,37,19,41,19,43,19,43,23,47,23,47,23,47,
%U A139421 23,53,23,53,23,53,29,59,29,61,31,61,31,61,31,67,31,67,31,71,31,73,37
%N A139421 a(1)=1; for n>1, a(n) = largest prime divisor of n!!.
%H A139421 Harvey P. Dale, <a href="/A139421/b139421.txt">Table of n, a(n) for n = 1..1000</a>
%F A139421 a(n) = A006530(A006882(n)). - _Michel Marcus_, Nov 08 2013
%t A139421 a = {}; Do[b = First[Last[FactorInteger[n!! ]]]; AppendTo[a, b], {n, 2, 100}]; a
%t A139421 FactorInteger[#][[-1,1]]&/@(Range[80]!!) (* _Harvey P. Dale_, Feb 15 2014 *)
%Y A139421 Cf. A010693.
%K A139421 nonn
%O A139421 1,2
%A A139421 _Artur Jasinski_, Apr 21 2008