Occasionally I wish I hadn't given away most of my math books, this is one of those occasions. I had a book with lots about partitions in it, but I long ago gave it away. However this problem is quite doable. The trick is to make P a function of 2 variables, first the number n you are interested in partitioning, and then the number i that is the largest number you are willing to partition it into.

With that tip, here is an answer in 90 characters: 

sub P {
my($n,$i)=@_;$i||=$n;$i-1?map{my$c=$_;map[($i)x$c,@$_],P($n-$c*$i,$i-1
+)}0..$n/$i:[(1)
x$n]
}

[download]

In reply to Re (tilly) 1: (Golf as well): List of Partitions by tilly
in thread (Golf as well): List of Partitions by jynx

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.