8 Dec
2009
8 Dec
'09
8:07 a.m.
On Tue, 8 Dec 2009, Richard O'Keefe wrote:
is_Zumkeller :: Int -> Bool is_Zumkeller n = let facs = factors n fsum = sum facs in mod fsum 2 == 0 &&
I see this test is essential. I didn't do it and thus my program did not find that 1800 is not a Zumkeller number within an hour. With this check my program becomes dramatically faster.
can_part facs (div fsum 2)
main = print (filter is_Zumkeller [1..5000])