Given a Natural number K, how many combinations [tex]\[(adsbygoogle = window.adsbygoogle || []).push({});

x = \left( {x_1 ,...,x_N } \right)

\]

[/tex] of Natural numbers vectors are there, so that [tex]\[

\sum\limits_{i = 1}^N {x_i ^2 } = K

\]

[/tex]?

I'm desparate and will believe anything... :yuck:

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# Combinatorics, I guess

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