#Is it true identity?
13 messages · Page 1 of 1 (latest)
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how would you define the $b_i$ more specifically? just saying natural numbers feels off.
dark matter
Reminds me, by considering, for integers $i_1,…,i_r$, such that their sum is $n$ the set $\mathscr{D}(i_1,…,i_r,n)$ which is the set of partitions $(I_j)_{1 \le j \le r}$ such that $|I_j|=i_j$ for all j in ${1,…,r}$ you can prove that $|\mathscr{D}(i_1,…,i_r,n)|=\frac{n!}{i_1!….i_r!}$
😑 ɿototoЯ | Rototor 😑
There is a nice proof using the natural group action of S_n on that set (that is transitive), calculating the cardinal of the stabiliser of one of the elements of the set and using the orbit stabiliser theorem
@round ermine
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