Stream: Beginner Questions

Topic: Reordering summations


view this post on Zulip Ryan Shao (May 06 2023 at 13:29):

Hello,

I have proved the following about reordering of summations on arbitrary functions:

∀r. (∑m::nat=1..Suc(r). ∑j::nat=0..m-1.  f(m, j))
= (∑j::nat=0..r. ∑m::nat=j+1..Suc(r). f(m, j))"

I want to show:

(∑m::nat=1..Suc(r-1).
               ∑j::nat=0..m-1.
                        list_sum(
                          (map (λy. (multinomial_term k (j#(m-j)#y)) * (prod_term (a # lis)
                   ((m - j)#y)) * x^j)
                          (generate (r - m) (length(lis)))))) =
              (∑j::nat=0..r - 1.
               ∑m::nat=j+1..Suc(r - 1).
                        list_sum(
                          (map (λy. (multinomial_term k (j#(m-j)#y)) * (prod_term (a # lis)
                   ((m - j)#y)) * x^j)
                          (generate (r - m) (length(lis))))))

Where the inner functions are the same. However using the lemma I proved previously and trying sledgehammer led to nothing. What am I missing?


Last updated: Apr 28 2024 at 04:17 UTC