Reciprocal Sums

*To*: mathgroup at smc.vnet.net*Subject*: [mg32472] Reciprocal Sums*From*: "Juan" <erfa11 at hotmail.com>*Date*: Tue, 22 Jan 2002 03:19:57 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hello, I need your help to resolve this question (I give a example for n=12): In[1]:= << DiscreteMath`Combinatorica` In[2]:= n = 12; In[3]:= p = Partitions[n]; Now, I want to get from p thouse partitions which reciprocal sum is a integer. In[4]:= r = Cases[p, x_ /; IntegerQ[Plus @@ (1/x)]] Out[4]:= {{6, 3, 2, 1}, {4, 4, 2, 1, 1}, {3, 3, 3, 1, 1, 1}, {2, 2, 2, 2, 2, 2}, {2, 2,2, 2, 1, 1, 1, 1}, {2, 2, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}} But, is n is a big number, then you have to wait a big number of seconds to get r. Any suggestion to do that better-faster? Best regard Juan _________________________________________________________________ Hable con sus amigos en línea, pruebe MSN Messenger: http://messenger.msn.es