Simple recursive assignment

• To: mathgroup at smc.vnet.net
• Subject: [mg15996] Simple recursive assignment
• From: "Peltio" <pelt.ioNOS at PAMiol.it>
• Date: Fri, 19 Feb 1999 03:27:10 -0500
• Organization: Peltio Inc.
• Sender: owner-wri-mathgroup at wolfram.com

```Can someone spare a little time for a trivial question?

The assignement
a[0]=1.;
a[1]=2.;
a[n_]:=a[n]=a[n-1]-a[n-2]/n
works fine, all right...
a[5]
0.291667

But how can I achieve the same results when the expression a[n-1]-a[n-2]/n
is stored in a variable expr? The following approach leads to a Recursion
Limit error
expr=b[n-1]-b[n-2]/n;

b[0]=1;
b[1]=2;
b[n_]:=b[n]=expr

b[3]
\$RecursionLimit::reclim: etc.

I tried a few combinations with Hold, Release, and so on but I can't fool
the recursion trap.I'm sure it's something trivial I'm missing
Any help would be greatly appreciated.
Thanks
Peltio,
peltioNO at SPAMusa.net

(remove NO SPAM to e-mail me)

```

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