# [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
1,2,2,1,2,4,2,2,3,4,4,2,2,6,1,2,2,4,6,4,2,2,2,7,2,2,6,6,4,4,2,8,1,4,
%T A144925
2,4,6,2,6,2,2,10,2,4,5,2,6,4,2,6,10,2,4,4,2,6,8,3,2,10,2,2,2,6,10,2,
%U A144925
4,2,2,2,10,4,4,7,6,6,6,2,10,6,2,8,6,2,4,4,2,2,14,1,2,2,4,2,10,6,2,6
%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
href="http://pachome2.pacific.net.sg/~cosmology/index.html">AQNT
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.