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Re: a[n],b[n]

• To: mathgroup at smc.vnet.net
• Subject: [mg104933] Re: a[n],b[n]
• From: fd <fdimer at gmail.com>
• Date: Fri, 13 Nov 2009 05:57:43 -0500 (EST)
• References: <hdgr4b$jc5$1@smc.vnet.net>

On Nov 12, 10:21 pm, ynb <wkfkh... at yahoo.co.jp> wrote:
> a[n + 1] = 1/4*(1 + Sqrt[5])*a[n] - 1/2*Sqrt[1/2*(5 - Sqrt[5])]*b[n],
> b[n + 1] = 1/2*Sqrt[1/2*(5 - Sqrt[5])]*a[n] + 1/4*(1 + Sqrt[5])*b[n],
> a[1] = 4, b[1] = 9.
>
> a[n]=
> b[n]=

I imagine you want to do some recursive function. In your code there
are at least three mistakes
1) you should use set delayed (:=) instead of =
2)you cannot include n+1 in the function argument
3) you have to use underscore in the function argument variable

A factorial function will look like this

a[n_]:=n a[n-1]

a[1]=1