       RecurrenceTable warning

• To: mathgroup at smc.vnet.net
• Subject: [mg102430] RecurrenceTable warning
• From: green tea <cetech07 at gmail.com>
• Date: Sun, 9 Aug 2009 06:05:11 -0400 (EDT)

Hello, I'm using Mathematica 7.0.1.

This example is in documentation center.

In:= RecurrenceTable[{a[n + 1] == 3 a[n], a == 7}, a, {n, 1, 5}]
Out= {7, 21, 63, 189, 567}

In:= RecurrenceTable[{b[n] == a[n], a[n + 1] == 3 a[n],
a == 7}, {a, b}, {n, 1, 5}]
Out= {{7, 7}, {21, 21}, {63, 63}, {189, 189}, {567, 567}}

it works well.
but when I simply swapped a with b, a warning occured.

In:= RecurrenceTable[{a[n] == b[n], b[n + 1] == 3 b[n],
b == 7}, {b, a}, {n, 1, 5}]

During evaluation of In:= Inverse::matsq: Argument {{1/4,1,-1},
{1/4,0,1}} at position 1 is not a non-empty square matrix. >>

Out= {{7, 7}, {21, 21}, {63, 63}, {189, 189}, {567, 567}}

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