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 A073840 #9 Dec 05 2013 19:55:31
%S A073840 1,4,24,192,4320,51840,120960,29030400,65318400,145152000,6706022400,
%T A073840 160944537600,8717829120000,6590678814720000,14122883174400000,
%U A073840 30128817438720000,2112783322890240000,2662106986841702400000
%N A073840 Product of the composite numbers between n and 2n (both inclusive).
%C A073840 a(n) is divisible by central binomial coefficients, A001405[n]
%F A073840 a(n)=A049614(2n)/A049614(n-1)
%e A073840 a(6) = 6*8*9*10*12 = 51840.
%p A073840 for n from 1 to 50 do l := 1:for j from n to 2*n do if not isprime(j) then l := l*j:fi:od:a[n] := l:od:seq(a[j],j=1..50);
%t A073840 cs[x_] := Flatten[Position[Table[PrimeQ[j], {j, x, 2*x}], False]]+x-1; prcs[x_] := Apply[Times, cs[x]]; Table[prcs[w], {w, 1, 25}]
%o A073840 (PARI) a(n)=prod(i=n,2*n,i^if(isprime(i),0,1))
%Y A073840 Cf. A073839, A073641.
%K A073840 nonn
%O A073840 1,2
%A A073840 _Amarnath Murthy_, Aug 13 2002
%E A073840 More terms from _Sascha Kurz_ and _Labos Elemer_, Aug 14 2002