122,801 reputation
478205
bio website math.ubc.ca/~israel
location Richmond, Canada
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visits member for 3 years, 4 months
seen 2 hours ago

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


8h
revised Optimum set partitioning with constraint
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8h
revised Optimum set partitioning with constraint
added 194 characters in body
9h
comment Optimum set partitioning with constraint
The question is nontrivial if $\sum_{i \in A} i \ge m$. For example with $m=5$ and $A = \{1,2,3,4\}$, an optimal solution is $\{1,3\},\{2\},\{4\}$.
9h
answered Optimum set partitioning with constraint
9h
answered Factoring in Maple
16h
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.
21h
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.
1d
answered Solution of the Legendre's ODE using Frobenius Method
1d
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.
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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