       Help ! complex permutations

• To: mathgroup at smc.vnet.net
• Subject: [mg6965] Help ! complex permutations
• From: Robert_P at pro-bel.co.uk (Robert Perkins)
• Date: Wed, 30 Apr 1997 22:25:30 -0400 (EDT)
• Organization: pro-bel
• Sender: owner-wri-mathgroup at wolfram.com

```I need to derive an algorithm, formula, which gives all the
possiblities, combinations, for any 'n' out of 'm' with the proviso
that any member of 'm' can be used multiple times and the selection
sequence is significant.

Taking a trivial example if the input list 'm' is

{a,b}

the output list 'n' for any 2 gives

{a,a},{a,b},{b,a},{b,b}

For an output sequence of 3 from the same input list would give

{a,a,a},{a,a,b},{a,b,b},{b,a,b},{b,b,a},{b,b,b}

Life gets interesting for larger input sequences and ever larger
output selections. How about the input list containing 10 members and
the output list containing 20 members with the above rules applying?

Can anyone point me in the right direction? A reference, clue or even
an algorithm would be very welcome ;)

TIA

Robert_p

```

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