Question 933617
<pre>
3n(2^n-1)

n   3n   2^n  2^n-1  3n(2^n-1) 
------------------------------
1    3    2     1      3
2    6    4     3     18
3    9    8     7     63
4   12   16    15    180
5   15   32    31    465
------------------------
             total = 729

Edwin</pre>