1,776 reputation
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bio website math.mit.edu/~shor
location Cambridge, MA
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visits member for 3 years, 11 months
seen Sep 12 at 10:57

Aug
4
comment $q|2^p -1 \Longrightarrow p |q-1$ for primes $p,q$?
Hint for first statement: use an elementary theorem from group theory.
Aug
4
comment Distributing half a deck of cards
This seems like an ideal problem on which to use the inclusion-exclusion formula.
Jul
1
comment Number of unique permutations of a 3x3x3 cube
Any arrangement can be rotated to yield 24 superficially different arrangements. You can put any of the six faces on the bottom, and then with that face on the bottom, o can rotate it to have any of four faces facing south.
May
18
answered Should I understand a theorem's proof before using the theorem?
Apr
8
awarded  Nice Answer
Mar
30
comment A confusion about RP class of problems
If the answer is incorrect, the machine will never accept. Thus, if the machine accepts, the answer is correct. It's the logical contrapositive.
Oct
14
awarded  Yearling
Oct
4
comment Why are certain greek characters used predominantly for certain purposes in mathematics?
@DonAntonio: my comment is meant to point out that this should really be treated as two separate questions: (a) why are Greek letters used in mathematics? and (b) why do certain letters get used predominantly for certain purposes?
Sep
28
comment Why are certain greek characters used predominantly for certain purposes in mathematics?
This isn't specific to Greek letters. Why do $f$ and $g$ always stand for functions? Why is $i = \sqrt{-1}$? Why is entropy always represented by $H$ or $S$? Why is $\aleph_0$ the cardinality of countable sets?
Sep
7
comment Why variance in probability is taken as E[(X−E[X])2]?
Why is this question being asked on cs.SE and not math.SE? Computer scientists did not define variance, and as far as I know, its usage in computer science is no different than its usage in math.
Aug
11
revised Number of partitions of n with k parts.
fixed formula so it would actually be correct, and made some no-op changes in formulas to avoid 6-character rule.
Aug
11
suggested suggested edit on Number of partitions of n with k parts.
Jul
9
comment Rectangular Ground with Square tiles
If $r\geq 2$, it is easy to prove that the minimum area has to be $81$ (since both edges must be at least $4r+1$). This is enough to show that the $r=1$ solution is minimal.
Jul
8
answered Rectangular Ground with Square tiles
Jul
4
comment Rectangular Ground with Square tiles
Clearly, the ground is $0 \times 0$. There are no red tiles, and no white tiles, and since $0 = 0$, this satisfies the conditions.
Jun
24
revised What will be time complexity using dynamic programming
found minor bug in my dynamic program
Jun
23
revised What will be time complexity using dynamic programming
fixed typo and explained why the first try didn't work right
Jun
23
revised What will be time complexity using dynamic programming
counted number of solutions
Jun
23
answered What will be time complexity using dynamic programming
Jun
22
comment What will be time complexity using dynamic programming
You seem to have made a mistake. If the sum of ten integers is even, the sum of their squares also has to be even. Thus, you cannot solve the problem as posed.