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May
25
comment “Casual” mathematical facts with practical consequences
The puzzle is to explain why these two differently-sized rectangles seem to be both partitioned in to the same 4 polygons. Knuth claims this was a favorite puzzle of Lewis Carroll (See "Concrete Mathematics", Graham, Knuth, Patashnik, pg 293)
May
25
answered “Casual” mathematical facts with practical consequences
May
25
revised “Casual” mathematical facts with practical consequences
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May
24
comment Is the factorization problem harder than RSA factorization ($n = pq$)?
The answer is trivially "yes" since you didn't limit computational power in any way, and factorization is certainly decidable.
May
23
awarded  Nice Question
May
23
revised How valid is the concern over narrow pipe cryptographic hash function designs?
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May
23
comment How valid is the concern over narrow pipe cryptographic hash function designs?
@Pete: Point well-taken. However, I prefer remaining anonymous on these forums, so I'll have to live with the loss-of-value engendered as a result.
May
23
answered How valid is the concern over narrow pipe cryptographic hash function designs?
May
23
comment Partial sum over $M$, of ${m+j \choose M} {1-M \choose m+i-M}$?
Although I don't know if your summation is handled by the methods in the following book, you might want to check it out. The methods here are often called "revolutionary" as regards summations of binomial coefficients: math.upenn.edu/~wilf/AeqB.html
May
21
comment Subset sum problem is NP-complete?
Yes, thanks. Corrected.
May
21
revised Subset sum problem is NP-complete?
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May
21
answered Subset sum problem is NP-complete?
May
21
revised What are a , b and c?
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May
21
answered Can a number have a prime factor that isn't a part of the number's prime factorization?
May
20
comment Another pigeonhole principle question
@Arvin: Yes, c(7,3) is correct. I was leaving that part for you to work out, but I see other respondents did the whole problem shortly after. Ah well.
May
20
awarded  Good Question
May
20
answered Another pigeonhole principle question
May
20
revised Preparation for Putnam?
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May
20
comment Logic Puzzle of the age of three sons
If the answer were 1,6,6 and the two 6-yr-olds were born 11 months apart, wouldn't there still be an "oldest"?
May
19
answered If $a|b$ and $c|d$, then $ac|bd$