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Jan
12
comment I've come up with two solutions to this problem, and I don't know which is correct.
Bah! How on earth did I miss that. Thanks.
Jan
12
asked I've come up with two solutions to this problem, and I don't know which is correct.
Jan
12
comment How to approach this problem of combinatorics
Nevermind! I was thinking for the general case.
Jan
12
comment How to approach this problem of combinatorics
Shouldn't it be 144? I believe you're missing a 2.
Jan
12
accepted How to approach this problem of combinatorics
Jan
11
comment How to approach this problem of combinatorics
So I shouldn't even be caring about what the actual products are? If I'm reading what you wrote correctly, this is almost like how many combinations I can make of 1 apple, 2 oranges, 2 pears, 1 kiwi, and 3 mangoes?
Jan
11
asked How to approach this problem of combinatorics
Jan
6
accepted Proof involving Stirling numbers of the second kind
Jan
6
awarded  Commentator
Jan
6
comment Proof involving Stirling numbers of the second kind
@BrianM.Scott Maybe it's assumed for all positive integers greater than equal to $k$?
Jan
5
comment Proof involving Stirling numbers of the second kind
@BrianM.Scott Yeah, I'm looking at it right now and it says, in italics, all positive integers x.
Jan
5
asked Proof involving Stirling numbers of the second kind
Jan
3
comment prove that $\text{rank}(AB)\ge\text{rank}(A)+\text{rank}(B)-n.$
Have you tried working out an example? Try a few by hand and see if you can generalize it. Or you can try showing it by contradiction; though I always feel direct proofs are much more clear.
Jan
2
accepted How to simplify this equality (factorials)?
Jan
2
asked How to simplify this equality (factorials)?
Dec
28
accepted Pigeon-hole Principle: Does this proof have a typo?
Dec
28
accepted If an integer is divisible by 8 and 15, then the integer also must be divisible by which of the following?
Dec
28
accepted How is this a property of Pascal's triangle?
Dec
26
awarded  Analytical
Dec
26
asked How is this a property of Pascal's triangle?