[seqfan] A144925: non-trivial divisors of composite numbers

franktaw at netscape.net franktaw at netscape.net
Sun Aug 30 00:31:53 CEST 2009

I'm currently editing this sequence.  What I have so far is:

%I A144925
%S A144925 
%T A144925 
%U A144925 
%N A144925 Number of nontrivial divisors of the nth composite number.
%C A144925 1 and the number itself are excluded as divisors.
%D A144925 Y. K. Huen, A matrix map for prime and non-prime numbers, 
Int J Math.
               Educ. Sci. Technol} 6: 913-920, 1994.
%H A144925 Y. K. Huen, <a 
               Project Homepage</a>
%F A144925 a(n) = A070824(A002808(n)) = A000005(A002808(n)) - 2.
%p A144925 numcompz(n):=taylor(sum(1/(z^i*(z^i-1)),i,2,n),z, inf,n)$
%o A144925 (PARI) k=1;vector(120,n,while(isprime(k++),0);numdiv(k)-2)
%K A144925 nonn,new
%O A144925 1,2
%A A144925 Huen Yeong Kong (cosmology(AT)pacific.net.sg), Sep 25 2008
%E A144925 Sequence extended by Juri-Stepan Gerasimov 
(2stepan(AT)rambler.ru), Aug
               05 2009

Edited and extended by [me].

I'm concerned about that "numcompz" (the %p line).  This occurs in 3 
different places in the current version; and if the comment about it 
being a Maxima statement function is correct, none of these is the 
right place.

But more seriously, it doesn't appear to be correct.  I don't really 
know either Maxima or Maple, so I don't know for sure what it does 
there; but what it appears to do is nonsense.  I can't make any sense 
out of any interpretation of it I can think of, either.

Can anyone make sense of this?  If  not, I'm going to delete it.

I also wonder about the link to Huen's home page.  I don't see anything 
relevant there.

Franklin T. Adams-Watters

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