Complete Solution:
The numbers can be rewritten as:
$1=1^k$
$45.2548=2^{5.5}$
$1262.6650=3^{6.5}$
$32768=4^{7.5}$
$390625=5^{8}$
$10077696=6^{9}$
$282475349=7^{10}$
$3037000499.976=8^{10.5}$
$31381059609=9^{11}$
Therefore, the $n$-th term should take the form of:
$n^x$
By Hint 3,
The author hints that the powers are actually consecutive font sizes in Microsoft Word! Thanks to @shoover in the comments for discovering the connection to font sizes! Also credit to @Stiv for finding the link between "Word" and MS Office first, though it was actually the hint gave it away to me.
The list of font sizes in the dropdown menu, in increasing order: 5 5.5 6.5 7.5 8 9 10 10.5 11 12 14 16 18 20 22 24 26 28 36 48 72 (largest font size in the dropdown menu).
Therefore, the last term is
the 21st term, and is equal to $21^{72}$ aka 158412417187039737963434604385921446947320760732675527347603818345931941295685218431561257343841
With that said, though, it should be noted:
There are actually two versions of list of font sizes in the dropdown menu! The version the @Ankit used seems to be extremely uncommon. The more common version, which is 8 9 10 11 12 14 16 18 20 22 24 26 28 36 48 72, is much more widely used. With this more common list of font sizes, it would have been impossible to spot the pattern!
Here is the screenshot of Word 2007 with the list of font sizes used in this problem (Source):