Hi,
How do I express (or approximate for larg $\displaystyle m$) the following sum in term of $\displaystyle k,m$ ?
$\displaystyle \sum_{1\leq i_1<\cdots< i_{k} \leq m} i_1i_2\cdots i_k$
Please help,
Thanks
I mean by
$\displaystyle i_1i_2\cdots i_k$
a product, so the expression represent a sum of all possible products of k distinct number between 1 and m. For instance k = 2 and m = 3
$\displaystyle S=1\times 2 + 1\times3 + 2\times 3$
so can't we express it more simply without the sum ?
Thanks for the helps.