Question 894675
<pre>
{{{(n+1)(n+2)(n+3)*""*""*(2n)}}}

Multiply and divide by {{{n! = 1*2*3*""*""*n}}} 

{{{(1*2*3*""*""*n*(n+1)(n+2)(n+3)*""*""*(2n))/(1*2*3*""*""*n)}}}{{{""=""}}}{{{(2n)!/n!}}}

Edwin</pre>