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bio website math.ubc.ca/~israel
location Richmond, Canada
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visits member for 3 years, 4 months
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I'm an Emeritus Associate Professor of Mathematics at University of British Columbia and an Optimization Algorithms Researcher at D-Wave Systems in Burnaby BC


Jul
22
answered Factoring in Maple
Jul
22
comment Choosing random marbles until one is divisible by $X$
The way you stated the problem, $X$ is always $1$: choose one marble and its number will certainly be divisible by $1$. If that's not what you mean, please explain what you do mean.
Jul
22
comment Solution of the Legendre's ODE using Frobenius Method
No. You can take $a_1$ to be anything. The recurrence then tells you want $a_3$ is in terms of $a_1$, what $a_5$ is in terms of $a_3$, etc.
Jul
21
answered Solution of the Legendre's ODE using Frobenius Method
Jul
21
comment Radius of convergence of power series
@Libertron That is indeed what it means. The radius of convergence $\ge r$ because the function is analytic in $\{z: |z - z_0| < r\}$, and $\le r$ because $|f(z)| \to \infty$ as $z$ approaches the pole, so you conclude it is exactly $r$.
Jul
19
awarded  discrete-mathematics
Jul
19
answered Matrix Algebra, Signs of solution
Jul
19
comment Find all positive integers $n$ such that sum of digits of $2^n$ is equal to $n$.
Yes, but the effect on most of the digits is very small.
Jul
18
answered Can Gomory's cutting plane be used to solve Mixed Integer Linear Programs?
Jul
18
comment Find all positive integers $n$ such that sum of digits of $2^n$ is equal to $n$.
BTW you might also mention some reasons the digits are not independent: their sum mod 9 is known, as is their alternating sum mod 11.
Jul
18
comment Find all positive integers $n$ such that sum of digits of $2^n$ is equal to $n$.
We don't. The most we can do is estimate the expected number of additional cases.
Jul
18
answered Inverse Laplace transform, none factorable denominator
Jul
18
answered Is there a function almost everywhere $0$ on $\mathbb{R}$ whose graph is dense in $\mathbb{R^2}$?
Jul
18
revised Lattice Path Spaces.
added 142 characters in body
Jul
18
answered Lattice Path Spaces.
Jul
17
revised Find all positive integers $n$ such that sum of digits of $2^n$ is equal to $n$.
deleted 17 characters in body
Jul
17
answered $n$-to-$1$ near zero of holomorphic function
Jul
17
comment $n$-to-$1$ near zero of holomorphic function
Do you mean, a holomorphic function that has a zero of order $n$ is $n$-to-one near that zero? That follows from the argument principle.
Jul
17
comment A definite integral involving $\exp(-a\cosh x)$
You should be able to take the first derivative wrt $b$, divide by $b$, and then take the limit as $b \to 0$ to get the case $n=1$.
Jul
17
comment How to prove that some set is a Borel set
It's not quite true that "it is not possible to characterize a Borel set". See en.wikipedia.org/wiki/Borel_hierarchy