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Jan
8
answered $\sum_{k=0}^n (-1)^k \binom{n}{k}^2$ and $\sum_{k=0}^n k \binom{n}{k}^2$
Jan
8
comment Number of strings of length 10 consisting of the digits 0,1,2,3 with even sum of digits
Oh yeah, my bad. What is wrong with me today?
Jan
8
comment Number of strings of length 10 consisting of the digits 0,1,2,3 with even sum of digits
but that's a good argument
Jan
8
comment Number of strings of length 10 consisting of the digits 0,1,2,3 with even sum of digits
The only characters available are $1,2,3,4$
Jan
8
answered Number of strings of length 10 consisting of the digits 0,1,2,3 with even sum of digits
Jan
8
comment Number of strings of length 10 consisting of the digits 0,1,2,3 with even sum of digits
your sum should start at $i=0$
Jan
8
answered A binary operation defined on a set with one element
Jan
8
revised Finding the shortest cycle in a graph using every edge
added 338 characters in body
Jan
8
comment Finding the shortest cycle in a graph using every edge
I got the minimum cycle length was $38$, $7$ edges where doubled
Jan
8
answered Finding the shortest cycle in a graph using every edge
Jan
8
comment Finding the shortest cycle in a graph using every edge
I think he thought you needed an eulerian path
Jan
8
comment Probability of Sets
I think I found a non too shabby proof that the numerator is $3^n$
Jan
8
revised Probability of Sets
added 472 characters in body
Jan
8
comment Probability of Sets
oh yeah, I think I saw it in a book, I'll try to prove it combinatorially to keep with the counting theme in the answer
Jan
8
comment A question about the orders of the elements of a group
I just meant that you don't need to know what the free product of groups is. You need to know what a free group is, but not free products.
Jan
8
comment Probability of Sets
this is better. +1, I'll leave mine to see how this is better.
Jan
8
answered Probability of Sets
Jan
8
answered cycle in a product of directed graphs
Jan
8
comment Permutation inverse form
Also, why does the permutation contain repeated elements?
Jan
8
comment Permutation inverse form
oh, here is a mathjax guide meta.math.stackexchange.com/questions/5020/…