Re: Factorising polynomials
- To: mathgroup at smc.vnet.net
- Subject: [mg63993] Re: [mg63970] Factorising polynomials
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 26 Jan 2006 03:43:44 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
data=Factor[x^Range[6]+1];
If[#===Expand[#],1,Length[#]]&/@data
{1,1,2,1,2,2}
If[FreeQ[#,Times],1,Length[#]]&/@data
{1,1,2,1,2,2}
Bob Hanlon
>
> From: "Tony King" <mathstutoring at ntlworld.com>
To: mathgroup at smc.vnet.net
> Subject: [mg63993] [mg63970] Factorising polynomials
>
> I am trying to find the number of irreducible polynomials over the integers
> in the factorisation of x^n+1
>
> I used the following code
>
> data = Factor[x^# + 1] & /@ Range[6]
>
> Followed by
>
> Table[Length[data[[k]]], {k, 1, 6}]
>
> And Mathematica returned {2,2,2,2,2,2}, one assumes because it was
counting
> terms such as 1+x as 2 terms. However, when the number of factors
exceeds 1,
> Mathematica returns them as a list and counts them correctly. The output
> that I was looking for should have been {1,1,2,1,2,2}.
>
> Does anyone have any ideas how I might modify the above code so that it
> returns the correct number of terms
>
> Many thanks
>
> Tony
>
>