[challenge] Hamming numbers

[Don]

bearophile wrote:
> Justin Johansson:
>> Bearophile, if you are reading this perhaps you might like
>> to repost some of you previous "challenges" which have not
>> received much attention with the [challenge] annotation in
>> the subject line.
> 
> See:
> http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=116505
> 
> Bye,
> bearpophile

That's not a very useful problem, because the timing depends entirely on 
BigInt, which is completely unoptimised for small values.