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Question: combinations on subsets

Question: combinations on subsets

Harry Garst 259 Maple
combinatorics
February 19 2019
0

This works fine, but I was wondering whether it could be done in a simple way.
 

``

> 

restart; kernelopts(version); interface(version)

`Maple 2018.2, X86 64 WINDOWS, Nov 16 2018, Build ID 1362973`

  

`Standard Worksheet Interface, Maple 2018.2, Windows 10, November 16 2018 Build ID 1362973`

 (1)
> 

kollect := proc (p::`+`, y) local x; subs(x = y, collect(subs(y = x, p), x)) end proc
> 

kollect(kollect(kollect(kollect(expand(add(mul(k)*add(k), `in`(k, combinat:-choose([i1, i2, i3, i4], 3)))), i1^2), i2^2), i3^2), i4^2)

(i1*i2+i1*i3+i2*i3)*i4^2+(i1*i2+i1*i4+i2*i4)*i3^2+(i1*i3+i1*i4+i3*i4)*i2^2+(i2*i3+i2*i4+i3*i4)*i1^2

 (2)

``


thanks in advance,

Harry

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